I was looking through all the posts (probably not all as there are quite a few) with which oil to use. Many recommend Valvoline 20w50 but it seems difficult to find in the UK especially on line when searches usually result in Valvoline Vr1 which says not for use on wet clutch applications. Others recommend Halfords Mineral oil, again when looking the only 20W50 appeared to be web only, Silkolene silkolube 20W50. So searching about on the net I found this site, cheaper than Halfords and it came the next day. I was also considering the classic mini oil which has a high zinc content and is ok for wet clutch.
https://www.classic-oils.net/