David,
Based on previous years, all drivers arriving in a classic or kit car are directed to the outside show area which has been right next door to the kit car inside area for the last couple of years, tin tops parking is outside the show gates.
Complete Kit Car are the organisers of the kit car area of the show, page 27 of the October edition invites applications for inside stands to adam@performancepublishing.co.uk. The inside area allocated to the Dorset Area is already fully allocated but you might be able to get Adam to extend it for an extra car (although the whole building has been getting fuller every year since the invitation was extended to kit cars). Cars on the inside area stands have to be on site before opening and can't leave until after closing so it can be quite restrictive.
It's best to buy tickets in advance as you get a 20% discount - link is posted above
If you're interested, the Dorset area are currently holding their monthly meeting at the Rest and Welcome Inn on the A37 at Melbury Osmond, DT2 0NF at 8pm on the first Thursday of every month, so very close if you're South Somerset based.
Jon