Thanks for all that help guys - I have now decided against the 18-135 and am veering towards the 55-200 VR, although I am still a bit undecided. One of my reasons for originally considering the 18-200 was that I would then only have to carry one lens around with me, especially while travelling. (I worry that I may miss the killer shot while faffing about changing lenses and am also neurotic about letting dirt in). If I get the 55-200 I would still have to carry the kit lens around as well and would also need to buy a bigger bag. Oh decisions, decisions!