I saw something that suggested that the BBC interactive service will give some coverage if you've got a freeview box. If that's true I'm going to buy one as they're fairly cheap
Some of it is on BBCi (I think the Cross Country and Dressage Highlights) and Grandstand is showing the 3 Day Event Show Jumping. However, I understand Eurosport is showing loads of live coverage of the other events. I think I read this on HHO somewhere!
I watched the showjumping on Eurosport the other day and yer man (who I can't abide listening to) said there would be huge coverage of the WEG on Eurosport - there was last time 'round anyways...