My wifes 1.2 52 plate Clio has just been fixed after it started miss firing and then refused to start after we pulled over.
Took it along to out local independant garage and he spent over a day trying to resolve the problem. The on board computer was throwig up errors re the injectors but this along with others were false reading. Eventually traced it back to a problemwith the main ECU. Looks like moisture gets in here, normally dries out but seems to have got onto the main board and has caused dry solder joints. He cleaned these off and resoldered and it started first time.
I guess at a main dealer they would have just replaced the ECU and charged big bucks.