You have as many injectors as cylinders. Have a look on your injectors they will probably be the same make as the pump.

Does it look like this one? : http://www.ebay.co.uk/itm/VAUXHALL-ASTRA-CORSA-1-7-CDTI-DIESEL-FUEL-INJECTION-PUMP-0445010086-/221210338661?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item338129e565

I think you have a common rail engine in whch case the pump is irrelavent to the number of injectors, it just keeps a a rail fed with hight pressure fuel to which any number of injectors can be connected, I believe yours has a four cylinder engine so will have four injectors. Are they saying that you need injectors as well? What is the actual problem with the car?

Thats an odd one. I assume the engine eventually stopped by itself. engine runaway is generally caused by fuel/oil entering the system other than by the correct route, possibly because the turbo seals have failed but as they haven't mentioned that I assume its not so.the other reason is that the engine is very worn but I wouldn't think that would be the case either, those problems usuallly give blue smoke and can end up destroying the engine so I am at a loss with your problem.

Reading the fault codes is a neccessity with modern cars as they are electronically controlled, the only advantage being is that it usually tells you what the fault is/was, that would be the ECU they would be reading.

You could try looking up a dedicated Vauxhall forum but other than that you are going to have to rely on your garage I'm afraid.

Peter