I looked into this myself just recently, I have opted for normal 95 unleaded and use 'Castrol valve master' addative.
Within classic car circles it gets consistantly good reveiws, if you google it you'l see what I mean. available from Hailfords £10 for 250ml (1ml treats 1 litre of fuel so 1p/ltr).
I've seen it cheaper but most are within a short distance of a Hailfords store.
There is a valvemaster plus (with octane boost) but you will not need that as old petrol specs put octane around the 70 mark.
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Stock......the new custom