Most digital SLR’s are still a bit more expensive than that brand new. Canon EOS350D is probably the cheapest Canon new at about £529. I think there is a Nikon D50 ? which is about £479 new.

For about £300 all you are probably going to get is a secondhand EOS300D which is still a very good camera capable of some very good results. I have mine for sale on E Bay at the moment having just upgraded to a 20D.

Good luck in your search.