OK seems to me no pressure at all on what you write, I take it the Fuel Tank has a couple gallon in [ have to ask Daz ] you see I want to concentrate at moment on the Cold start injector, that's on the main pressure line, Black/yellow is LIVE + Daz only with Starter turning ONLY, its know as circuit 50 , its not fused, its also on the Thermo timer...check there you will see Black/yellow again , has wires been "cut " there, The brown will be to earth,but aware not now from timer..... Forget metering unit at moment, once pressure returns Cold start injector sprays direct into manifold, it must Fire up, all be it stop after 3 seconds having used up the Fuel from injector, also Note the Cold start injector is completely separated from both ECUs...your starter does crank...so the missing circuit is there, could be cut at timer ? make sure plenty petrol, useually pumps screem / become noisy when almost out of Fuel. your test of pushing metering flap...pump running..would have give plenty of Fuel. Peter