Darn it, looks like I'll have to buy some carb cleaner!

If the SAI pump is what I think it is, a low sort of grumbling noise in the background for about a minute or two when starting up, then I'm not sure that's the problem. It seems to start to happen at the same time it shuts off when firing up from cold, but if warm then it's running a bit rough and gets lumpy very quickly while the pump is running.
I'll keep plugging away and check all the sparky bits and go and look at this SAI pump thing too.
By the way, the paperclip test gave fault codes of 31 ( no engine RPM signal, so disregard that one) and 57 (Idle Air Control Voltage Low).