REAL race circuits :confused:
What, as apposed to pretend ones?
I don't think that you've considered this idea properly.
An example: Chris Y, a Ten-Tenths member, has recently taken his ARDS course. This course is to get you the necessary National Class 'B' licence to race on UK circuits. I think the course required some instruction, but I'm not sure. It certainly involves an expensive medical examination.
Once Chris had earnt his licence, he paid for a drive with a professional Mini Seven race team. I think the day, which consisted of practice, qualifying and racing, cost him over £900.00
That is before you've even looked at a car, RACMSA-approved racewear, safety equipment and the like.
Scrutineers at MSA events tend to be a little more strict in my experience, so the standard of car preparation is required to be that much higher. Entry fees are considerably higher (Like £150.00-ish), and you are unlikely to be competitive in any car described as 'cheap'.
If your only requirement is to drive 'round a
'REAL' UK race circuit, I suggest you pay for a trackday or take some instruction at one of the circuit driving schools.
You asked about cheap racing, and it realy doesn't get any more so than Autograss racing.
If you want National circuit racing, I'm afraid it will be anything but cheap.