The CFS badge was indeed applied to the first Hawks to arrive at Valley, but the badge shown in the photo was a later version that did not emerge until 1981. The first aircraft to have this version applied was XX181 and I took a photo of it the day it first came out of Gaydon Hangar.
It is quite correct that down on Sparrows we had whichever aircraft were available each morning, but we did manage to get five CFS-marked aircraft one day, and I got them lined up next to each other for a photo.
I left Valley in mid 1985 and no blue-topped aircraft had appeared at that time.
Incidentally, if it is of interest, I have probably the only shot of a grey/green camouflaged Hawk with very short-lived 4 FTS markings. This was at a time when there were plans to rotate the 4 FTS & TWU fleets, and it was the first such aircraft to arrive. There must have been a very rapid change of heart, because it quickly went back to Brawdy.