Update: Ohmigod I love PCWorld!
According to the casio website the only way to deal with broken camera is to send it to the casio repair centre. According to the teeny tiny printed words on the little folded up warranty sheet in the camera box the second option is to take it to the place of purchase: PCWorld in my case.
Took it down there. Told half the story (it went dark with lens stuck out, took out battery and put back in and it retracted, now won't come out again). Didn't mention any dropping or forcing. In fact when I was telling the guy how little use it had had, I told him I'd bought it slightly less than a month ago (true) but only actually used from last week (true) and that it had seemed fine (true) and I was at home taking a photo of my dog (slight fib) when it had stopped working, I also said, that it hadn;t been anywhere exciting and hadn't had anything exciting happen to it.
He looked at it, told me this was a very common thing to happen. Then checked stock and said they had no more left. There was the possibility of taking a black one instead (£20 more than the green, which I'd have been happy to pay) or getting a different camera. I thought about it and said I'd really liked the camera before it stopped workng and would very much like the same model and whilst i was totally in love with the green colour, I'd rather takle a black one than a different camera... unless this was a particular problem with this model, in which case maybe I had better get a different one....he said it was a common problem with all of these kinds of cameras not just the casio exilim. He said if I really wanted the green one I could maybe pick up from a different branch. Since the other branches were all miles away I was going to just get the black one, but then asked if there was any chance of the other branch sending a green one to this store. He made a couple of phone calls and arranged for a new exilim green to be sent out to him. Should be there within a week. He's going to phone me when he has it. No additional charge to me
Quibble-free replacement. I really wasn't sure I'd get that. I was talked into trialling the 'anything goes' service for my PC when I bougth it, but I didn't take the option on the camera (extra 1.99 per month) so I figured they'd just say they had to send it away and I'd end up with a bill.
I love PCWorld. Of course I won't completely relax until i have it in my hand *grins* just in case he was mistakenly looking at the part of my receipt that said 'anything goes club' and thought it referred to camera rather than laptop. But I don't think that was it.
*sighs* lesson learned and apparently at no actual cost!