get the eTrex from Garmin - the cheapest one. About 150 quid, available from Maplin and FieldnTrek, and lots of other places - I blagged mine from the office, as we had a customer who wanted location aware handhelds

It's cheap, accurate and tough - loads of amazing features, that take ages to get into, but blow your mind.

don't rely on it too much, otherwise you're stuffed when the batteries go. Get a nice Silva compass too ...

RG