I'd been having some starting problems recently, which I traced to the starter solenoid.
I replaced the starter motor (and solenoid) and that's solved it. It turns over much faster and catches immediately.
Winter starting can be a bit tricky when using vegetable oil as a fuel, because it is quite thick and needs a good strong pressure to pump it through, especially when the weather is cold.
In winter I put an additive called Coldflow 350 into the fuel, to prevent it freezing or waxing. I've just started putting it the tank again for this year, in case we have a cold snap.