I believe there is a classic car show on Bank Holiday Monday - 31/05/10 
The location is Berkeley Castle in Thornbury, www.berkeley-castle.com
I haven’t been there, so if anyone has, please let us know if it’s worth going to.
I’d seen that one advertised lynne but website doesn’t give much detail, would like to hear more about it too.
We went to this today,so for future ref…
There was a good mixture of cars from really old to ones young enough for me to remember! including a Lamborghini Countach. Also autojumble and antiques.
No MX-5s on show, though saw a couple in car park.
The event was held in the meadow, so a bit bumpy for anyone who has lowered suspension. The entrance cost was £5 per adult and we were there for just over an hour.