Hi Wilf,
I'm actually using Castrol Valvemaster plus which is supposed to add 2 Octane as well as protecting the valves.
I'ts also supposed to be compatible with LRP RON95 and RON97 (Optimax as well I guess)
The engine has been re-built at least twice as far as I know. Once by Metaline in 87 - 89. A second time in 92 when a crane cam was added.
I'm actually in Shepshed, which is near Loughborough, near Leicester, In the middle of England, near Europe, On the planet Earth... I guess I'll stop there
Paul