I think I might have got it.
Method: at the CWGC site, look for WW2 casualties between 1941 and 1943, and use filters to restrict to Polish and Air Force with a memorial in the UK. This gave me a list of 555.
Sort the list by cemetery/location, pick out the churchyards and do a Google search for pictures. (I have a browser add-on which allows me to do this very quickly, and as most of the casualties are in cemeteries rather than churchyards it wasn't such a long list.)
The one I've come up with is Henlow, Bedfordshire, where there was a single Polish burial - Jan KLIMCZAK, who died on 28 Jan 1943. CWGC record is at
https://www.cwgc.org/find-war-dead/casualty/7503678/klimczak,-jan/The page gives a bit more about where he was serving.
There's a bit about RAF Henlow at
https://henlow-pc.gov.uk/raf-camp/ but I haven't looked into this or a possible Polish connection.
The church in our photo has a few distinctive features: large buttresses on tower (shown by shadows), castellation round the chancel roof, and a tall chimney on the north aisle/vestry. Henlow seems to have all these:
http://www.henlowchurch.org.uk/st-marys.htmhttps://bedfordshireparishchurches.co.uk/wp/henlow/And the closest view I could find to the one in our photo:
http://mayflowerhistory.com/tilley-john/EDIT:
Jan KLIMCZAK's memorial at Findagrave:
https://www.findagrave.com/memorial/31076044/jan-klimczak