I think Southend might be a better "beach" location than the cliffs near Eastbourne.
I am just guessing from the map above, but my hunch is they have used town names the public will recognise, and for routing from Duxford "Colchester" will be the VOR at Clacton (actually some way inland), "Southend" is the NDB on the airport there, "Maidstone" will be the VOR at Detling, and "Eastbourne" will be the VOR at Seaford. The great photo just above seems to bear this out - they have come directly above the clifftop Seaford one, which is just out of shot to the left.
I did go to Gosport beach for the 50th in 1994 (seems like yesterday), there was a significant ship display in Spithead, but I remember more a somewhat off-programme display of a formation of maybe 20 glider tugs, pulling about 20 gliders, nothing historic but likely from Lasham or somewhere, coming overhead about an hour before the official events started. Anyone here involved ? You got quite a cheer from the beach.