In reply to Beth-Cath-T:
We cycled in from the carpark between Dovestones and Yeoman Hay reservoirs the other week if that's the one you mean.
It takes less than 15 mins (just under 2 miles) and is a reasonable gravel track, a tourer bike would be ok, a roadbike a bit dodgy.
We ditched the bikes on the side at the end of the track, but you could carry them up the hill slightly and put them behind the wall. Could always take a lock to secure the wheels, it's too far for anyone to want to carry the bike out.