I have a 2003 1.4 tdci fusion, and the engine has started cutting out whilst driving. The engine cuts out, the battery and oil lights come on, then it cuts back in again. It has done it at 70mph on the motorway which is a bit scary, but it also has done it whilst sat stationary in a queue of traffic. One time it didn't restart, so I got towed to a garage. They diagnosed it needed a new alternator, but it has continued to cut out since the alternator has been replaced. I'm at a loss to what could be causing it, I can't do without a car, but similarly I can't afford to be spending loads out on trying different things.....

. Reading through similar past posts there have been issues with the fuel filter causing similar problems.

I was surprised to read that they have a 37k ish / 3 years change interval.

If it was electrical issue i would imagine it throws up a fault code, did the garage that diagnosed the alternator carry out a scan / read for errors ?

There was also a post recently about a dodgy earth for the ECU - This is a single wire connected directly to the battery -ve connector (at least on the petrol) so may be worth a look.

I will have a look at mine when i pick it up from garage (maybe tonight) as it's just passed the MOT after replacing headlamps.

maybe that one or maybe on the ecu itself

Sound like a bad battery earth to the chassis or engine. Could cause battery light to come on. With the engine running try measuring the voltage between the battery negative and the engine block. You should get around 0V. Carefully try using a piece of wood to gently move the wire harnesses to see if you can repeat the problem. 

That Blue/Black one (at least, that is what it looks like).

Kevin's is a good idea.