Shanthi, have you looked into joining British Eventing? You can usually get discounts into events as a spectator.
I've joined as a volunteer, and wouldn't mind volunteering for events (that are on the weekends, anyway, there are a lot of weekday horse trials here!). The trick is getting to the events, though.
Excellent
London 2012 should be a blast. I got to go to WEG and watch the cross country because my friend lives very close to the horse park, so accommodations and food were provided. It was so fantastic to see! I bet London will be great, too - seems like the big international events are getting more and more insane (in a good way, I think?) each year.
I meant to watch the WEG this year, and totally forgot.

I bet it was super fun to see in person, though!