Paul Goy racing on the Allenby estate or there's a place in Waddington that's supposed to be ok too. I know where it is but can't remember the name!!?? :-[
As for power gains on the valver, K&N panel filter with full exhaust should give you a bit and/or get the head polished and ported. Volkskraft in Fiskerton did the work on mine and are pretty reasonable on costs too