haha, probably won't be tombs this time. according to the program I have it'll be Bentley Priory which is somewhere close to Harrow. Volunteers will be working on the marsh area, the dell, the stream or many of the glades dotted around the site' (from the booklet I have) check out the calendar:
http://www.btcv.org.uk/cgi-bin/office_opps_ind.cgi?ref=106®ion=lo
they have a dragonfly pond!! how cool.