Is that auto solo stuff or actual sprint events?
I'm taking things one step at a time at the moment. Get car track prepped then I need some track time under my belt before considering budget anyways to be honest.
I do the Javelin Sprint Series (been doing it since was a Toyota only series in 2008) They are sprints but they aren’t governed by MSUK. Events are run by Javelin Trackdays who set their own, fairly open, technical regs (no deciphering of the blue book required) and the events are licensed by the IOPD (Just a small one of payment for either an annual or single event licence as appropriate).
If you just need seat time then trackdays are better value but personally I get bored on a trackday lapping with no purpose and really enjoy the competitive element that sprinting brings with it.