Thank you chaps – tad embarrassed that I didn’t try the Dunlop site first as it’s not long since I used it to ID another tyre. .oops! So we’re at a point where the tyre is certainly of the type fitted to Britannia 200 series but the rim which is definitely an AH40xxx would seem to remain a wildcard. I’ll do some work on the stamp and report back.
Thanks very much for everyone’s help so far 🙂