Now I wouldnt like to comment on those whitworths (although I may know a man who would)
As to my trade, we are not Gunsmiths as such, we do learn to weld, and can be trained on lathe work.
The basic armourers course is 9 months long, 3 months in the classroom studying materials science, engineering maths, some physics, tech drawing, then its into the woekshop for a month of handskills training (so many of our younger generation never did 'shop' at school, computers. Yes, hammers & files no!)
After that its into basic principles of firearms, the cycle of operations etc, bit on ballistics, then its onto the weapons phase, pistols (semi-auto only, BHP &226) rifles (SA80 family, L96 sniper & the new .338) MG's (FN GPMG & Minimi), mortars, chain gun, 30mm RARDEN cannon ( and the turret systems, inc sights)
All of these phases include complete component strips, rebuilds, fault finding, inspection standards and the 'action of mechanism' for each weapon.
On the 'class one course' taken around 4 years later its 6months long, and is almost the same course, but more in depth inspection and higher standards.
Also added into the mix then are the 105mm light gun and examination of ordnance (inspecting the big stuff)
Then theres all the little courses whenever something new is introduced, .50MG, grenade MG, remote weapons systems, Javelin etc etc.
Mainly a glorified parts swapper these days, we'd get sued to death if I manufactured a new sear and something went wrong!