Thanks to you both. The rear rim is definitely wider then the front (~3.0″ vs 2.5″ outside width) so I’m a bit baffled why it has a 3.25 section tyres on both front and rear. Clearance doesn’t look like an issue so I don’t know why the correct size rear was not fitted. My current preference is for more modern section tyres so I’ll have a look at the Road Riders. The budget option appears to be Mitas tyres – can anyone comment if they are any good?
I do not know if the rims are standard sized or not which obviously doesn’t help. I would appreciate any advice as what tyres I could fit as I have effectively no idea what people fit to “old” bikes. I would prefer good handling and grip to a “period” appearance. I would certainly rather avoid a Speedmaster rear as I hated the feel of that on my dads Speedtwin (why on earth did someone think it was a good idea to design a rectangular section tyre??).