My suggestion for what it is worth is get in touch with Ian Hambridge - he and his very hard working group at Maiden Newton put on an excelent event this year and the location prety much fits the bill for the type of event that you seem to be outlining.
So there you go - Maiden Newton, Dorset. fantastic village, amazing history and a lot of war time fortifications still in place all allong the line of the railway. They even get the road closed for the weekend.