The problem is that you don't want to just "throw parts at it" until you find the cause (as we say here in the States).

Maybe you have an intermittent crankshaft ignition sensor, but I sort of doubt it. I think their usual failure mode is to go completely dead forever.

If it really is a fuel delivery problem, I think what a mechanic would do is to crack some fuel lines before and after the fuel distributor to see if fuel is getting there, but I don't recommend that you do this yourself unless you really know what you are doing. Maybe you have a bad fuel distributor, but you don't want to replace it unless you are sure it is bad because it is very expensive.