ACW, you are right about the low level. I saw surprised to see in my log book that I flew Bomber Command Routes 21, 23 and 24 in 1964 but by 1965 we moved in to the UK Low Level Route. My last Bomber Coomand low level was BC/21/R followed by BC/23/R with just one RBS attack.
From this I guess 21 was the west coast and 23 the esat coast terminating at Newcastle for a 2E.
Looking on I see we did a route from EP1 on the south coast to the Ouston Gate. If memory serves, there was a short cut across the north of England.
Moving on, Gernish bombplot was, I seem to remember, the relocated MRBSU from Glasgow. Lovely spot
. Hated the targets there, one bit of rock always looked like another.