Is there a lift pump in the fuel tank?

We had similar symptoms with a diesel Xantia, at first an intermittent failure then no go at all. In tank pump; first only occasionally then a permanent fail.

Thanks for the replies, all. I should have specified, it's a petrol engine.

Yes, it was the same key.

I agree that if it's running normally there may be difficulty in identifying the cause. I'm just nervous about driving around thinking that the engine might cut out again.

In the end, the Citroen garage couldn't look at it til december, the independent garage said they would look at it tomorrow, so I'll try taking it there and see if they can see anything (if it makes it there)

Thanks all

For what it's worth I spent 12 years as a roadside patrol with both major motoring organisations, and 15 years as a main dealer technician before that, and I can tell you this from experience. Roadside patrols see vehicles broken down first hand. Garage technicians generally do not. They only see the aftermath of what's happened. If the RAC patrol could not find the fault when it occurred then I'll guarantee you your garage will not find it when everything's working as it should. As unsettling and as inconvenient as it may be, your best chance of finding the problem is to wait until it does it again and call the RAC again.

Yes they did - it was various things to do with "x not found" and the RAC guy said he thought it was a fault with the on-board computer