Dear Flakdodger (Dave),
Most of the information you kindly offered I did have already because I began researching this all over a decade ago via the MOD and at Kew, but new things turn up on-line month by month. The internet is such a treasure trove nowadays, but can be dangerous if you don't check primary sources too. I suppose I'm lucky that my original research came before stuff was "out there" and has been confirmed by other web-sites.
So, very many thanks for the leads you have suggested.
Over the years I have seen the information publicly available on 300 Squadron links but was worried about naming others, wasn't sure of the ethics of that. There were family conversations about the two who shouldn't have been there in the Wellington but they were often in a "don't tell the children" hushed tone.
I had almost given up on taking this thread any further until another link (with someone who was a pilot) made me think again of other ways of moving on. Then the Channel 4 programme about 303 Squadron last week made me even more determined to locate the crash site, as a matter of respect, if it's possible.
I visit a family grave in Suffolk every few years so a detour through Lincolnshire would be manageable one day.
I will check all the leads you have suggested.
Thanks for your time and careful thoughts,
Again, Celia