Stotfold, Silverstone, DMS and Herts are the midsouth area clubs holding the 'regional' series this year,
http://www.oople.com/forums/showthread.php?t=61900
I am sure you would be welcome at any of these meetings, need to be BRCA member, first 4wd Stotfold on Sunday, may be worth looking in at to see how these meetings work, expect a few B44's (I am not sure you would be allowed to race, BRCA membership needed, but club meetings usually allow a meeting or two before you are expected to have joined).