Ford Fiesta engine still running but no power from accelerator

I dont know where to begin with this car, we have had it for 2 years and it seems as soon as the warranty ran out EVERYTHING has started to fail. I am currently writing a letter of complaint to Ford about it all. The car started with the speedo dropping and not going above 20 MPH even though you knew that you were doing say 50MPH. Then the night before last it started doing the same thing only this time, the engine was still running but there was nothing happening when I pressed the accelerator. I had to get brakdown out to get it home. Yesterday morning I arranged for my garage to pick it up and they deemed it undafe to drive, they investigated it but it came up with unlisted fault codes and so they had to get in touch with Ford. I went down to Ford and explained what was going on and he said that it sounds like it might be one of the main computers that is breaking down, now, I dont know much about cars but, this to me sound rather expensive and surly when the car is not even four years old yet, the main computer breaking down isnt just wear and tear. I am at my whits end with it all, I have already had to pay out to get the EGR valve replace and rewired and the ABD front sensor replace which didnt solve my ABS issue, I am begining to wonder if all the other issues are related to the computer issue. I am so angry! Does any one have any advice for me and should I be complaining to Ford, they left me stranded last night with no car as they said that they didnt have a courtessy car available.