I have just received in the post some books I ordered from the Formula One Register, including one which covers Formula Libre events in Europe from 1929 to 1961. I opened this briefly and flicked through some pages, and lo and behold, there it was..........
The Cowap is not pictured in Ireland, so my hunch was way out. In fact the photo is taken at the start of a race at Snetterton on 3 May 1952 (I did not attend at this meeting ,my home track, as I was only 20 months old). It is entered by J A Cowap, driven by A Black, and is powered by a 750cc supercharged Austin 7 engine. It is red in colour, and according to the very short notes in the book , it was formerly raced by Ken Jarvis.
So the puzzle is now completely answered.