Recently Laura made a post with some of these signs, so of course I had to go and have a look at them and make one myself. Obviously, I'm not British, but I recognise all of these, and can relate very well to some of them. Maybe they could be called "You know you've been in Britain too long when..." as well.
Anyway, here is my selection! The rest can be found here.
and my personal favourite:
I'll be doing one for Scottish things soon!