I've registered for a trackday run by motorsport-events.com. I've never gone with this company before but their events look like really good value. They're run on airfields and perimeter roads rather than real race circuits so that keeps the price down. Their Heyford Academy Day 1 is held at a former US airforce base near Bicester and is mostly driving exercises and training rather than a full-on track session. That's perfect since I still don't know how to balance my car when I'm at the limits of traction. For £99, it seems like a good deal to me. Here's a write-up of a previous event run for the Caterham 7 club. This event can be followed by a level 2 Academy Day with more advanced training. If Day 1 goes well, I'm quite sure I'll sign up for Day 2.
If you want to join me, it's on Saturday, March 19th. I hope it's cold and wet. If it's cold, it helps cool the car. If it's wet, you get less tyre wear and lots of practice with understeer and oversteer.