It controls all the internal electrics to the vehicle.. 'apparently'... lol
At first the problem looked like it was a crank sensor.. so we replaced it, but no joy. Then we thought maybe a cam sensor, but at £85, main dealer part only, i wasnt prepared to just buy it and see. So then the car was put onto a fault diag. machine.. where it said 'faulty power to the ECU'.. ???
Well its now booked in at my local dealer, first thing tomorrow morning.. I'll post up the results, as no one on here seems to know anything about it.