BW, thanks for the leads. Could you give a little more detail on Raven, as my inept fumblings with the search button have not bore fruit.
A bit more searching reveals the use of 'buzz' numbers derived from the ac type (in this case FW for Super Sabre) and the last 3 of the serial number. I have found a lot of references to Triple Zilch, and she seems to be the subject of many pictures, but so far I have not found out why this particular ac should have so much attention focussed upon her.
By the way, no-one seems to know how the painting came into the family's possession, and there are no family conections with the services, other than their proximity to several Stations in Norfolk and their operation of a light ac off a farm strip many years ago.
Thank you, M.