powerhouse marine does marine 2 stroke oil, take your own container and they'll fill it, it's propa gear not cheap rubbish you get from supermarkets for a couple of quid (it's about £5 per litre if you take your own container).
I read somewhere the main difference between normal 2 stroke and marine grade is salt repellent properties, duno personally how much truth there is to it, but personally I'll stick to using propa marine grade.