I'm looking at investing in a Sony A200 soon, as much as the range of Sony lenses may be limited it mustn't be forgotten that the Sony alpha cameras can use old Minolta lenses which can be found cheap on eBay (and from reviews I've read they are wonderful lenses!).
With reference to your budget:
Sony A200 (with kit 17-70mm lens) : £260 (amazon)
Camera Bag (a whole different kettle of fish!) : ~£50
CompactFlash memory card 4GB : ~£25
And as far as lenses go the Sony 55-200 (SAL55200) gets very well reviewed : £130 new
Also the old minolta lenses are supposedly very good, primarily the 'beercan' 70-210mm and 'big beercan' 75-300mm. I'm not 100% sure of the prices of old Minolta lenses but I have a few 'watched' on eBay so will let you know.
If you are considering Sony then the best place for reviews of cameras and lenses (Sony, Minolta, Tamron, Sigma) is www.dyxum.com
I hope this was useful, possibly best to take my enthusiasm with a pinch of salt as I don't actually own an A200....yet. I'm waiting for my exams to be over!!