Looks like we were posting at the same time Erich ! That's a good start, it looks like it would have been UP- H, a MkVI. The Squadron converted from MkIIs in July 1943, and there's a very good chance the serial number was in the HJ*** range,
for example, HJ790. I don't know if the Squadron ORB is accessible on-line, but I'll have a look. Failing that, I can also look in my own stuff.