Ford Fiesta eac fail

Hi just wondering if you can help at all? I have a Ford Fiesta zetec 1.4 Petrol 52 reg. I broke down last week as I had a “eac fail” come up flashing on the dash. My breakdown came out and put the computer up and it said throttle body. My dads mechanic mate has changed the throttle body and it was still coming up with eac fail and when he tried to put the accelerator down it wasn’t reving to full power but said on the computer it was 100%. It come up on the computer that there was a problem with the accelerator pedal so hes replaced that and he did get it working eventually and it started revving right but then he turned the engine off and turned it back on and it went back to eac fail and not revving right. He then locked the car and unlocked it and started it up and it was revving fine again but then turned it off and tried again and it went back to eac fail. My dads mate recons it needs a new engine control unit (ecu) now. I’ve already paid £100 for the new throttle body and electronic accelerator pedal with labour of fitting it. Any advice would be greatly appreciated. It’s my first car only had it 6 weeks. Hoping it’s not going to cost too much more or I’ll end up having to get rid :(