You'll be wanting something with decent zoom for sports, which puts a dSLR out of your budget because although you could get one for £300 you'd need a telephoto lens on top which would be at least £100 and probably considerably more - I guess you could manage it if you bought second hand, but I'm not sure a dSLR is really what you're after?
So you're probably looking at a bridge superzoom, something along the lines of a Fuji S-series, Sony H-series or Canon S3 IS.
I havent really looked at these sorts of cameras in while so wouldn't like to say which is the best option, but they all have their fans (I had a Sony H1 for a while which was a very nice little cam).
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www.dpreview.com for reviews and user opinions on their forums.