I did a 'taster' session on Saturday at 7pm and it was great. Haven't ridden a fixed since I was about 8 years old, so it was an odd mixture of excitement and nervousness – and great to have that mixture about getting on a bike, which is never the case nowadays. The sessions are for 16 people in the group, and you're taken through a period explaining how to ride – technique like slowing down, getting on and off the track, so the actual time whizzing round the track is probably half an hour or so, I'd say.
The steepest part of the track looks daunting (at 42 degrees) but you soon learn you have to produce "more power Igor!", to get round it the higher you go.
The bikes are from Condor, and the shoe cleats for clip-ins need to be Look Keo. If you don't have them don't worry, they have cleated shoes you can use or, if you're wearing trainers, they have cages-with-straps that sort of 'clip-on' the Keo pedals.
Would I do it again? Yes. It's obviously more fun if you're with a couple of mates though.
I did 'forget' to keep peddling a couple of times, but fortunately when cycling round the track at a sedate pace, but the sudden jolt soon makes you buck your ideas up!