Not that i know anything about cave photography, but i wouldn't shop in Dixons.
Getwet - Try shopping in Sheffield at Harrison Cameras 01142760002 on London road. Great for second hand gear from flashguns and cameras of all types. They are also good for new stuff too. And whats more the staff know exactly what they are talking about, not that the crap they woffle at you in Dixons. Give them a try.
As for cameras i would have a look at the Ricoh Caplio GX8. It is an awesome little compact digital camera boasting 8.24 million pixels which will mean that you get an 8 megapixel sensor. Big enough for A2 enlargement. It has a acurate 28mm wide angle lens. An external hot shoe so you can use a seperate flashgun. It is primarily an automatic camera but has a maunual function, so you can turn the built in flash off and use your external flashgun maybe on a 1 meter cable to provide some side lighting for your foreground subjects. The size of the camera is small enough to carry without worrying about it, for those off the cuff snap shots.
Not a bad price either!
Leica also make quality compact digital cameras but more money.
Canon IXUS range are all very good too.
Take a look at their website www.ricoh.co.uk/cameras/
Best of British!