I know its a dangerous thing but I assume the photo was taken at 203 AFS , Driffield ? Thanks to Keith Wilson-Clark of Air Britain and previously Valliant and Victor tankers at Marham I/he can add the following ;
FMK-Q was WA591 from 24.11.50 recoded XD during 1951 but not sure of the month
FMK-K was WA632 from 1949 until May 51
FMK-P was VW479 until 15.02.51 and doesn't seem to have been replaced
FMK-L was VW474 until 14.01.51 , then replaced by WA727.