Hi David,
More info if you haven't already come across this. Attached are online BSA catalogues I've found for 1950 (the 2nd catalogue posted has just a paragraph for the Gold Column listed at the bottom of a page below the Golden Flash bicycle) ...
What's really fascinating are the high-end components that the bike originally came with plus the optional deluxe frame finish that could be ordered. You could get the frame with optional chrome head lugs, fork ends and chain/seat stay ends.
And the bike came standard with dural (aka duralumin - an early aluminum alloy) chainwheel, handlebar, stem, seatpost, quill pedals with dural cages and lightweight drilled spindles, plus what has now become something super rare is a Brooks B37 saddle with a dural alloy frame.
While those old original BSA cantilever brakes and the 4-star BSA rear derailleur it could have come with have since been generally regarded as very poor for their time of 1949 & 1950, the rest of the bike was a serious racing competitor back then. And some might look down their sharpish noses at this vintage bike as just another factory bike when compared with the pricey artesian hand-built frame bikes of the time, but try comparing this bike to the best of anything being built at that time. It was BSA bicycles crafted just like this that ended up leading to the later BSA team and individual wins in the landmark Tour of Britain races of 1952 and 1953.
Your bike is truly worthy of a full restoration! If you wish, upgrade the brakes and/or rear derailleur to be period correct for the 1950's and all is OK. You'll be doing your part to preserve for future generations a key piece of UK bicycling inovation and craftmanship.
Gregory