[Acropolis]

It could be a few things, first of all how long has the car been sat for?

The fuel could have gone off and caused a small bloackage in the fuel line, more than likely near the tank end, which would mean it is been starved of fuel which would account for the engine not ticking over and running properly when not been revved.

It is worth checking the air flow meter and all the air pipes to make sure that there is no crap in there, leaves or anything like that can cause havok with them. The air flow meter should be in line with the air pipe somewhere, it will have the main air pipe attached either side of it and will have a rectangular black plug coming off the side of it.

It sounds to me like the battery has had it, it can sometimes happen when they are left standing for a while, and there may have been something draw a current from it when the car was left stood, which under normal use wouldnt be a problem, but with prolonged periods may cause a problem. Check the battery voltage with a multimeter and see what it is sat at, it should be somewhere around 12.8-13.2 ideally, but should start the car with anything down to about 10.5v in it, if the battery is flat put it on charge with a proper battery charger, (if you havent got one halfrauds do one for about £20 and always worth having), once it is charged, check the voltage, then leave it over night and check the voltage again in the morning. If the voltage has dropped a then the battery is knackered and should be replaced, shouldnt be too much for a corsa battery depending on where you go, if you need a new one go to a local motor factors, you will get the same if not better as halfrauds at a fraction of the price.

If the voltage doesnt drop over night, reconnect it to the vehicle and start the engine, then using the multimeter make sure that the alternator is charging the battery, as if it isnt then this would cause the battery to go flat as it is having to power all the electrics for the car as well as the engine, not so much a problem on a diesel as the engine doesnt really use much electric but on a petrol the whole engine is based on electric.

It might be worth taking the plugs out (if it is petrol) and making sure that they arent too dirty, heavy sooty deposits would indicate running rich on the mixture.

If none of this proves any use, then take it out for a spin, stop somewhere more than 1/2 a mile from you home and call out The AA or The RAC, and they will more than likely get to the bottom of the problem for you, they might not be able to fix it, but they should at least be able to tell you what the problem is, you can then decide where to go from there, either do it yaself or take it to a garage.

I doubt weather it is anything to serious, and i wouldnt have thought it would be the ECU they are fairly resistant to abuse, i have seen em drowned in water and mud whilst attached to vehicles and keep on working fine afterwards.

Hope that is of some use.

You also have a PM.