[Liam O'Neill]

Almost all those big white lenses you see at every major sports event, as used by almost every pro in the field (though not all) are Canon's. If thats where you are headed, I'd go Canon now.
Sure, they also tend to hang £4000 worth of IDs Mark II off their £4000 500mm white lens with another £4000 of camera/lens around their neck as a backup/closer zoom, which is all a long long way out of your budget, but if you go Canon now, you can build up to that later in steps as needed. If you go for something else, you may find later that you need to dump everything and start over with the Canon stuff, which will be expensive.

So you buy the 350D now, but the 70-200 F4 later, get a "more pro" body after that (which eventually becomes the backup), then a few months later get a 70-200 f2.8 IS (which eventually becomes the "other" lens on the backup body) then get the 500mm prime, then later still the latest top-of-the-range 1-series. Steps.