Some information about Mepal itself, the units based there (75 Sqn seems to have been the main one), links to a Google Earth image (not much left now!), and to the image of the Watch Office (since demolished) here:-
Stations-M
We used to use Mepal as a joining fix for Oakington (5FTS) in 1962/3, given its location near the end of the "Twin Canals".
Chug