Fred, you're correct in your conclusion that in the 50s many UK riders used to use their bikes for many a purpose, and it was a lucky cyclist who had more than one bike..and often the second bike would be either a training/riding-to-work machine, or a road/path with track ends and the front fork drilled for a brake. This type of machine would serve as a grass track machine ( in those days many local fetes had grass track races with the riders racing around the cricket pitch boundary), sometimes as a hard track/indoors machine, and sometimes as a general-purpose winter hack iron complete with mudguards..this being why many of the 50s "track frames" had mudguard eyes.
Although time-trialling was a very popular sport in the 50s I don't remember any move towards shortwheelbase models expressly for that type of racing. On the contrary most of the SWB frames, such as C.Bulters with a curved tube, the Saxon with its twin tubes, the Hetchins with a fluted tube, the Baines "Gate" etc were designed to accommodate a mudguard within the the slightly shortened rear end. In those days there was a frame that often took my eye - the GRANDEX, with its pronouncely curved seat-tube (see CR "British Isles pages)..and I suppose I assumed that this was an out-and-out time-trialling frame.
Among the riders in my own club, we tended to have a well-balanced do-everything road frame with a wheel base of 41.5/42", 73/71 or 73/72 angles, drop-outs with mudguard-eyes..even a lamp boss on the front fork. On such frames we did everything, Sunday club runs, mid-week training rides, cycle tours and holidays, Youth Hostelling. In the West Riding of Yorkhire, as eslewhere in the country no doubt, it was quite customary to ride out to a Hostel on saturday, complete with Carradice saddle bag, leave the Hostel early on Sunday morning..ride out to the time-trial or road race, dismantle all the unwanted accessories such as mudguards, saddle bag, saddlebag support etc..and then race. After the race was over..back on went all the accessories..and off we would go to cycle back home. In this manner you would often cover hundreds of miles in a weekend..and that was often all the train ing you managed to get...just miles and miles of riding. The better-off..or perhaps more dedicated or just simply better riders would carry their "racing wheels", more often than not "tubs" on a pair of wheel carriers attached to either side of the front axle, and secured to the handlebars with toe-straps. And not a single piece of lycra in sight!
Norris Lockley...spending too much time down memeory lane, these days...Settle UK
More often than not, unless you were lucky, the same back was used for the same purposes in winter, but with the gears replaced by a fixed sprocket