Back when my employer was a technical partner of TOCA there were a couple of seasons where I got to every round. Unfortunately for my bank balance I fell head over heels in love with Knockhill as a spectator venue, so normally now I get to all the rounds at MSV circuits (their 4 wheel season pass is incrediible value if you have the free weekend time to really use it), plus Knockhill and sometimes Silverstone.
If you have never been to Knockhill I strongly recommend it - I make a long weekend out of it, a mate of mine and his wife have it as either the start or end of a week's holiday, but however you do it it's well worth the trek north of the border. I only bother with Silverstone for BTCC if there's nothing else going on at an MSV track, and even then only because I only live about 40 minutes drive away...
It's a good venue if an event can really fill it (I love the Silverstone Classic) but for anything smaller it just feels soulless. Not as bad as Rockingham used to be though, IMO.