could you not find a 19" wheel that looks the part and with the same spindle dia,then a case of making wheel spacers to centralise wheel and a caliper relocation bracket thingy,is this some master plan you have here martin?
If i was still in the workshop, yes! I had a thought on making it more `off-roadable` without going the whole hog with a 21" wheel. BTW, do you know there is a bike breakers in Keynsham/Saltford, so i am told?