well what a struggle that turned out to be; the battery had gone completely flat, as a result the car couldnt disabe the alarm system and so the alarm kept sounding whenever we tried to do anyhing, including charging the battery. Got round it by jump starting the car letting it run for a bit (alarm still going at this point!) Turning off the engine and then turning the key in the drivers door to disable the alarm. I think the engine turning over for a while gave the battery just enough juice to register the key turn and shut it up!
Egr change completely solved the low power problem and the vagcom cable and fiatecuscan let me clear the error codes. Am currently sat waiting at an mot station, fingers crossed, it will pass. A huge thanks to everyone for their help; the community support here is great. If there's anything i can do to help out in future,as unlikely as it is what with you knowing a whole lot more than i do, just let me know.