[embee]

Sounds like your "mate" just gutted the fuel pump for you.

I have a Quill T3 and it doesn't need re-jetting, stock carbs do fine.

Sounds like a general good going over is called for. Like most of these things you can't just diagnose it as being any one item. You need to work through it and make sure everything is correct and serviceable.

As the others say, however, coils are a good candidate along with other components of the ignition system. You also need to thoroughly check out the carbs, chokes returning properly, water in the tank etc etc.