On Thu, 08 Oct 2015 09:59:12 +0100, Stephen wrote:

Is there anything I can try to resurrect it? The oil/petrol mix has been
in there a while, should I pour that out and start again?

Definitely. Two-smoke mix separates over time, apart from anything else,
so you'll have some really oily fuel at the bottom and plain petrol at
the top of the tank.

It's probably a bit gummed up in the carb, and maybe the pump diaphragm's
gone hard or even torn. But it really shouldn't be hard to get going.