I instructed at Manby from July 71 till it closed in Nov 73 and all the JP's were Mk4's. The School of Refresher Flying Course was a basic 30 hr Course; although some did a 45hr Course - for example ex Shackleton Pilots earmarked for the Nimrod who had never flown a Jet. We had a new course every fortnight (25 Courses a year) and there was a high emphasis on low level flight -so fatigue life usage was far greater than at a Basic FTS.
When Manby closed the role of Refresher Flying was transferred to Leeming. Apart from the PCL
we had to contend with flying our sorties with whatever was to hand - be it Mk3, 3A, 4, 5 or 5A. This could make Briefings somewhat interesting as the Student may never have flown that particular Mk before and a formation could contain more than one mark.