Thing is from what I can work out there were two size's.
26.4 which Campag have used for ages and 27mm which most UK frames used up until around 1975 (may have dates a little out). Then every one went 26.4 apart from JIS (Japanese Size) which is 27.
Now they are crown race inner diameters, but from what I can tell if you had a 27mm crown race you would also have a slightly different size head tube i.e the cups would be different.
So if the cups I have fit the frame it should mean that the crown race that came with it should also fit, which is a 26.4.
Unless for what ever reason Raleigh used a 27mm crown on this frame.
I will get the crown and crown race checked tomorrow, it may be a case that the race needs to be pressed on some how. Worse case I will have a little bit removed from crown so the race fits.