Hey! MarkW! That's my name you've got. Hope you're not my body double or a stalker.
Nicky. Serious advice; don't ever keep any camera in a plastic bag. The problem with sealed plastic bags is that, while they can keep water out, they can also keep it in, and while a camera might survive a drop of rain, it's much less likely to survive a plastic bag sauna. Yes, Buy a pukka camera bag; they're always remiandered in bins in Jessops once a year, and if not I'm sure fleabay has something.
A proper bag will have some shock insulation, be keep the rain off and, most importantly, will let your camera breathe if it gets damp. If you want to dry a wet camera, give it a mop down with a teatowel then put it UNDER a radiator, where the cool air currents will do it gently.