Thanks for your thoughts guys. All useful stuff for a returnee.
Faussy - I didn't know what the manufacturers recommendation was, so thats hugely helpful.
It all kind of stacks up. I collected it in the car, by pulling the front end off and rolling it back into the hatchback. In doing so about half a litre of unburnt oil tricked out the silencer/front pipe joint. If he's been running it at 33:1, that's likely a touch too much.
I also recognise its an old one likely with a bit of wear in the bore.
I'll start off at 50:1, take it gently for a while, and see how it pans out. Fingers crossed.
Insurance and tax now all sorted out. Working away from home this weekend, so looking forward to getting back for a play!!