Thank you, everyone, for lots of useful information and feedback.
Your replies have given me plenty to consider. I think my next step will probably be to have a look at some macro lenses and the G10, have a play with them in a camera shop, and see how I feel afterwards. As most of you have pointed out, I'll have to invest a reasonable amount whatever choice I make, so it makes sense to take some time to think through my options.
Thanks again, all!
