The UK is a difficult market and it won't change anytime soon especially with GAME pulling the strings off all the games for any collectors edition stock.
In the US they have target, best buy walmart etc all competiting and wanting the business, in the UK Tesco, ASDA, Sainsburys and other retailers aren't that interested in most games just the FIFA & COD which they do deals for when you spend cash in store not with the rest.
Amazon are Amazon and people will continue to use them for reliability and prices, they don't bother much for any collectors editions and then the smaller stores like Simply Games, Gameseek, Game Collection just can't afford to bring the collectors edition stock in, they generally get enough to cover them just over their pre-orders and they can't hold a big backlog like GAME can.
If you follow some of them on twitter, I think The Game Collection have mentioned they won't carry some games if they can't get stock & sell them at a ''competitive'' price, the most recent being the Nathan Drake Collectors Edition.