If this is an air cooled two cylinder engine as fitted to mature lifeboats, I used to start one daily for a year in 1971 in temperatures from -20deg C to +30 deg C. I was the junior Marine Engineer on a ship and everybody hated this job especially since the lifeboat was in the davits and the ship was at sea rolling like a goodun.
Thanks for the advice. As I said above a blowtorch isn't really an option and there are no leccy supplies (its on a buoy in the middle of a lake). I'll get someone to give me a hand and if it still doesn't go then I'll come back next week with some easy start.
I may be making a mountain out of a mole hill as I know the staff member who told me its a pig to start does struggle to start it anyway (bad back or something).
Give me a ring at Gunthorpe today and we can talk about it.