Where do you buy the 'crap, comics and bits of tat'? Do you go to the shops for something to do? Can you not go to the NT place with out going in the gift shop?
Maybe stop going to the shops if they inevitably lead to you buying things you don't need?
Tell the DC that the gift shop is closed?
Is your house full of crap, comics and bits of tat? Could you do a car boot sale to have a clear out and make a bit of money?
Is this a 'we don't know where all our money goes' post?
On Shop Well for Less (look on BBC Iplayer to see if there are any episodes available to watch) they sometimes mention toy, game and even lego libraries, plus a craft warehouse place where you could buy bags and bags of all sorts of craft bits for pence.
The toy and game libraries, you paid a small monthly sum to borrow toys and games, so the DC always had new things to play with, but you could keep swapping them for new things, and it was much cheaper than buying new all the time, and didn't fill your house with things you don't need. Can you get comics at the library - or electronically?