The Clubsport (BiDuro) activity is significantly different from the Prosport / SR3 (Enduro) with regard to cost.
The BiDuro series is probably at the high quality / high cost end of competitive non-promoted 'club' racing. A 30 minute test, 15 minute qualifying and two 45km races is £400. A well maintained second hand Clubsport goes for approx £12-£15k. Assuming you are a DIY type (i.e. look after your own car)you would probably need about £1200 per event to cover entry fees(£400), a set of Avon slicks (£470), race fuel, oil, brake pads, chain etc. The big variables are in any additional testing, the cost of your race transport, prep/maintenance and any repairs!
The Enduro series attracts the really well-funded - much more track time - but two drivers can share all the costs - say, a £40k SR3 and a min of £3k per event - plus testing!
As for driving - both series attact serious racers - so there is no chance of 'pot hunting'. Ros Kaiser, a 21 year old with a seriously impressive F.Ford, F4, National Karting background is not a pushover in the BiDuro series - which attracts the likes of ex F1 driver, Martin Donnelly.
The Enduro series attracts a number of well funded semi-pro expert racers like Nigel Greensal and Michael Vergers, and even they get beaten by some of the very talented regulars.
There is a huge spares truck at each meeting, so you never have to waste your weekend because you broke something - you can nearly always fix a broken car. Spares aren't cheap - but you can expect them to be available at that critical point.
National B only - so always a mix of experienced and novice drivers - full grids - and a seriously competitive series for both. By the way, all the pricing / regs is on their website at
www.radicalmotorsport.com