Renault Clio II (02) going into limp mode?

My car wouldnt start on New Years Eve and the brteakdown service told me it was the starter motor. I had it taken to a garage and it wasn't the starter motor but they couldnt find fault and sent my ECU for testing which cost me £200. I was then told that the ECU was ok and although they hadnt fixed anything my car was suddenly starting. I collected it and drove about 26 miles and then my car went into limp mode, i had to keep turning on and off but managed to get home, then the next day when i drove the same distance it happened again, this time when i turned off and back on it shut down every couple of minutes.

My car was tested by AA twice and showed no faults and has now been in another garage for 4 weeks and is showing no faults when plugged into computer.

They are now saying they will have to check all the wiring, i have been without my car for a couple of months and seem to be paying for nothing!!!