The light should just come on as the ECU gets power. So i'd look at the fuel pump/ecu relay first. If you know a bit about reading wiring diagrams and electronics you'll know which pins to short so you can ckeck without getting a new relay first.
The engine revving up could proberbly be another problem. Read the fault codes once you get it sorted.
The Fuel pump/ECU relay is usually attached to the bulkhead in the engine bay. But i'm guessing you're talking about a red top in a corsa, so that depends on where the fitter put this relay. I would think it's in the same sort of area though?
I turned the ignition on and all the lights came (oil etc) on except the engine management - I flicked the ignition on and off and the light came on and the car started.
I then flicked it on and off a few times and every time it took more attempts to get it to light and now it wont light at all.
The fact that it was intermittent, albeit over a very short period seems to make the relay the answer (a fuse is normally working or not) but I have changed the relay in the bulkhead and all the others in the fuse box seem to be lights / washers etc