Oh my gosh yes my DS (same - 18mths) is exactly the same!!!! I hate it - we sometimes have to hold him down to get the nappies on and its awful!

We're in cloth but I'm contemplating switching to pull-ups as well, just for the ease of whip 'em off, whip a new one on.

MIL says he's fine (she looked after him a bit before Christmas) as long as she gives him something to distract him but that doesn't seem to work for us!

I hear ya! I remember my DD went through the same thing but she was easier to be stern with - "Lie still for nappy change!" - whereas DS doesn't seem to care! With DD we ended up using pull-ups for a bit til she got over it, then went back to cloth.

Good luck!