CEX (international chain) and one of the pawn shops occasionally have a couple of examples of massively overpriced 16 bit era stuff, maybe the occasional NES game, and a handful of the cream of the crop PS2/GC/Xbox games behind glass (Skies of Arcadia gamecube for something like £110 the other week when I wandered through one).
For the most part though every game selling shop around here has nothing older than the PS3, 360 and Wii at this point and as of the last year or so those shelves have been shrinking at pace too. If there is any xbox or PS2 stuff then it is pretty much guaranteed to be sports games, the handful of pedestrian driving games, pedestrian shooting games or other games that you would expect to fill the shelves of charity shops and such like (you say share pictures I was actually thinking of making a thread for what features in your local charity shop/goodwill).
Handheld? Hahahaha. Maybe some loose GBA cartridges if you are lucky, few loose DS and 3ds too.
For retro stuff it is pretty much online, dedicated retro conventions/fayres, random chance in charity shops/antiques shops (see my master system pickups the other day
https://gbatemp.net/threads/things-you-recently-bought-or-got.347639/page-692#post-9573817 ) or the occasional stall at a car boot sale when someone does not realise what they have and treats it like a similar vintage toaster (a rarity in this world of ebay making it easy to see, and you have to get up very early for the sharks as they are termed seem to aim to be the first there and through).
I would not really expect much in the way of shops in the UK these days either; difficulty in obtaining stock (days of people wanting shot of things from their attic/basement ended some 20 years ago), quality of stock (they are toys and also now decades old electronics), volatility of pricing, fairly high price of entry meaning you have a somewhat discerning market (adult with my own income sort of thing, you are not getting intro retro with a paper round where you can play all the second hand modern games you want on that) and also needing to do the usual overheads (rent + the council tax bump for year 2 means nothing cool lasts more than a year and any selling locations are chain shops, coffee shops and charity shops).
