In 2010 with Derby Phoenix it was £120 per day (the club don't advertise one day entries but they will take them). For that on Saturday you get practice and two races. A second class - which would be the 175 - 675 Allcomers - is £30 and for that you get a 15 minute qualifying session plus a race. So for £150 you get 5 sessions on track.
Race distance is usually about 20 miles. Number of laps depends on the circuit but at Cadwell it is usually 8 laps - which believe me is plenty.
Sunday we have been getting three races and no practice. If you do Sunday only, if there are only a few riders, they have been put out with the 675 qualifying to get their practice.
Most clubs do an F400 NG, Wirral etc (apart from Thundersport though you can run in one of their other classes not sure which one though) but only DP attract a significant number of 250's, it being the home of F250. As such you get to race for two trophies - F250 and F400 as we all run in the same race - it is win win
