Continued:
Introduced in the middle of 1952, the new Senior 3.5" x 20" was heavily-built and first painted in a shade of dark green, with later examples - by far the great majority - in grey. Widely advertised until the late 1950s it was, with the exception of the simple, split headstock bearings, modern in concept with the drive coming from a built-on all-V-belt, built-on, 3-speed countershaft unit with a self-locking cam-action lever for tensioning (as an option, 2-step pulleys could be fitted to motor and countershaft to increase the number of spindle speeds to 12). In line with other contemporary makers, full enclosure of changewheels and drive system was provided (usually, but not always, by covers in cast aluminium) and the ground-finished, 4-inch wide bed was deeper and heavier than that on an ML7 (though with exactly the same design and dimensions of flat top and narrow-guide square-edged shears - it's even possible to fit the tailstock from an ML7 or Super 7 should the need arise. In some cases, the Granville bed appears to have been hardened, though no evidence of this being offered as an extra can be found. A cross-slide with four T-slots was fitted as part of the ordinary equipment, with the very ML7-like top slide pivoting on a spigot and clamped down through semi-circular slots at front and rear. Screwcutting was by changewheels (nine of 20 D.P. being supplied), a tumble-reverse mechanism and a 3/4" by 8 t.p.i. Acme-form leadscrew - though no screwcutting gearbox was offered until the short-lived Star  version of the early 1970s. The apron carried step-down gearing to engage a bed-mounted rack with the "single-pivot" leadscrew clasp nuts resembling those as first used on the South Bend 9-inch lathe.
Running in split, phosphor-bronze bearings (with red-fibre inserts in the slot to reduce oil leaks and provide a solid surface to bolt down to), the headstock spindle carried a Myford specification threaded nose of 1.125" x 12 t.p.i. Both spindle bearings were the same length - 19/16" - with the front a relatively large 13/4" in diameter and the rear 13/8". Backgear was of the simplest kind and just slid into position; the connection between bull-wheel and drive pulley on the headstock spindle being by a pin with a spring indent retainer.
Fitted with a No. 2 Morse taper socket, the tailstock spindle was locked by a proper compression clamp with the upper section of the unit able to be offset on the base for the turning of slight taper. The assembly was locked to the bed by an eccentric cross shaft with a captive handle.
A very rare Granville was the "Hi-Speed", this having a headstock spindle running roller races and different bed and tailstock castings. From its appearance it appears to have been an early version of the plain-bearing Senior and only one example is known - and that resident in South Africa.
Unfortunately, the Senior was priced at an uncompetitive £68 - some 40% more expensive than the contemporary Myford ML7.  Naturally, with such a handicap it too, like the later "Junior", failed to match the sales success of well-establish "7".
Originally produced with a 3.5" centre height, by late 1954 the lathe was being offered as a 4-inch model - though for a while both machines were advertised using one catalogue marked 31/2" &  4" Heavy Duty Centres Lathes.  Although the makers produced a generally a sound engineering job, they were guilty of cutting corners and neglecting details: the finish was poor, the castings being largely left as delivered from the foundry (though from the early 1950s onwards there was a considerable improvement); there was no facility to adjust the clearance of the tailstock locating tongue, built-in oiling points were scarce, the underside of the saddle lacked oil grooves and both top and the cross-slide feed screws run in directly in the relevant castings - all these points being correctly attended to on the Myford.
Items supplied with a new Senior included: a 9-inch faceplate, a 4-inch catchplate, a spare 4-inch chuck backplate, 11 screwcutting changewheels, a leadscrew swarf guard, a stellite-tipped hard centre for the tailstock, a soft centre for the headstock, the necessary spanners and Allan keys and a screwcutting chart. The usual range of extras was offered including fixed and travelling steadies, a swivelling vertical milling slide (that looked very Myford-like), machine vice, angle plate, graduated handle for the leadscrew end, a thread-dial indicator and extra changewheels to extend the threading range including a metric translation wheel of 127 teeth..
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Continued:
Upon the introduction of the new Senior lathe, Granville renamed their existing machine the "Junior, but this was replaced, in 1954, by the 3.5" x 18" New Granville Junior, a type that has always been comparatively rare on the second-hand market. This model was designed much more along the lines of the Company's "Senior" lathe and featured a No. 2 Morse taper tailstock, tumble reverse, a built on all-V belt countershaft unit and with both changewheels and backgear covered by cast aluminium guards. Spigoted into the bed with a rectangular tongue (along the lines of a Myford 7) the headstock of the Junior carried a spindle running in half-split bronze bearings and bored to allow a 5/8" diameter bar to pass through. Six speeds were provided, between 60 and 720 r.p.m. whilst the spindle nose (11/8" x 12 t.p.i) and leadscrew thread (8 t.p.i 5/8" diameter Acme) were both identical to those used on the Myford 7 Series lathes - with which, upon examination, you might notice it shares several other design "clues".
Eleven changewheels, from 20 to 65 teeth, were provided for screwcutting. The gap in the bed could accommodate a job 10" in diameter by 2.25" thick; although V-belt drive was fitted as standard to the headstock, flat-belt drive was available as an option for those inclined to think it the better choice. Accessories included plain and swivelling vertical milling slides, 4-way toolpost, machine vice, leadscrew handwheel dial thread indicator and various sizes of angle plate.
Although relatively short at 39" overall, because the countershaft top was angled steeply backward at its top the lathe was, for its size, an unreasonable 28" deep front to back. The lathe could be supplied in several forms: with and without both the countershaft unit and backgear assembly and with a choice of either V or flat belt drive. Its selling price, unlike that of the more expensive Senior model, closely matched that of the ML7, its closest competitor.
Another lathe sold by Corbett was their "XL", but this was just a surplus-stock Winfield with the maker's name crudely chiselled off the bed. An example is known with paperwork supporting the fact that it was purchased in 1950, two years before Winfield's  bankruptcy. However, it is possible that either surplus castings were being sold off, or the company had ceased trading some time before the conclusion of legal proceedings to wind up the enterprise. 
Details of the Granville "Star" lathe here.
Granville also marketed and badged the Centec 2 milling machine as their own, using a particularly heavy cast-iron stand - one quite at odds with the fabricated affair offered by the parent company.
Tony Griffiths

Grayson lathe badged during the early 1950s  for the Corbett Company of Sutton-in-Ashfield, Nottinghamshire, as a "Granville" Model CSL2. This version was fitted with all-V-belt drive and other minor refinements.  The lathe was also sold carrying Warwick badges.

From the maker's catalogue of the early 1950s - a  very rare assembly , the 3.5" and 4" Granville Senior mounted on the maker's cast-iron stand. See this page for a photographic essay of this "Senior"

Simple step-down gearing to engage the hand traverse with the bed-mounted rack and clasp nuts resembling those used on the South Bend 9-inch lathe. Note the bed-to-saddle gib-strip adjustment screws on the back of the saddle that, unfortunately, set the clearance directly onto the main tool thrust face.

The rare "Corbett's" 4 1/4" x 20" XL lathe. This lathe is an odd mixture of early Winfield (clustered backgear) and Pools Special (apron and cross slide end bracket) and would almost certainly have been manufactured by F. Coles of London

Another "Corbetts" - but with no maker's or supplier's marking -but almost certainly by F. Coles & Company. Note the headstock spindle and pulley arrangement - quite different to the version above with the small brass badge. 
More pictures of this version here