Trackday rubber for a novice

I'm about to undertake my first full trackday (Llandow) in a seven type kitcar as a novice and was wondering about tyre choice.
I've got hold of a spare set of wheels 5.5x14" (to save my normal tyres)which I'm going to shod with some suitable rubber.
Trouble is I don't want to go to the expense of spending hundreds of £££££'s as I'll only be doing 2-3 days a year.
I've heard that the cheapest solution is to use very worn normal road tyres. Is this true ? or am I going to make an arse of myself ?
If true which ones should I look for at my local part worn emporium?
Next cheapest solution is some used purpose made rubber (yoko's or Avons) Which ones and where from?
If I get the bug and want to do more events then I'll smash that piggy bank and get some new hoops !
Cheers
Clanger

We run road tyres on our car for the track and worn is best. New rubber with a lot of tread can get hot and all the rubber moves around a little.

For the Pirellis P6000 (and P Zeros) about 3mm of tread seems good (in the dry). Although I use a very different car - much heavier and more power - quick(ish) on the striaghts, slow in the corners (the opposite of yours?).

At first I'd go for a cheap reliable option. Buying a good set of (almost) racing tyres will be wasted on you (no offense). When you get into it see how you feel.

P.S. Welcome to ten-tenths, I hope we get to hear about your experiences here soon. :beer:

Thanks Adam
Part worn's it is then.
Cheers