Having found this thread I went thru my slide collection of Chippies.
Not checked your original list but did note that I have WK518 in three different schemes.
Red/White no codes
Silver with blue band just before the tail
Current BBMF colours.
Not sure where the Red/White one was taken as the slides dated 1999 so not at Manston where I was a pax in her in 1977. Silver one not dated but may be Coningsby before getting the black colours as a load of RAF vehicles in the background but again would have been after the Manston days.