Thanks Wojtek and Gnomey, got some various software, but just up-graded today, and trying to figure out the differences! I'll get there eventually.
Lucky, yes, Shell House was used as Gestapo HQ, Copenhagen. The raid was at the request of Danish Resistance, took place 11.15 hrs, 21st March '45. The painting, measuring 30x40 inches (76x100cm), was done for the 50th anniversary, and made into limited-edition prints to help raise funds for a memorial to aircrew lost on the operation. The prints were signed by surviving aircrew, S.O.E. agents and Danish Resistance vets, on the 50th anniversary, in Copenhagen. I had a fantastic few days there, with the vets, and visited Shell House of course, where a dedication ceremony took place, and other areas related to the raid, including the Commonwealth Cemetery. I've just finished writing and illustrating an account of the story behind the painting, the raid, and the 50th celebrations.
BTW, thank you all for the kind comments re. my work.