My parents have this old fashioned view that you should stop Guising (the Scottish equivalent of trick-or-treating) at about ten, which is what they made us do. Apart from going to a special event last year, I have'd celebrated Halloween properly in years.
But it not as much of a big deal in the UK as it is in the US anyway (Christmas is more important). I know in South Africa, it's even less so, as I addressed in my recent drabble (*ahem* self-promoting *ahem*) and according to my cousin, they don't even bother in Finland.