Sounds like the lambda sensor.

Isnt that a gearbox sensor?

No it reads the emissions (oxygen content) in your exhaust pipe, may have come loose but if it needs replacing they're pretty cheap and you don't need OEM parts, cheaper and quick enough to have sent from UK by post I'd imagine.

edit: If this fails your fuel mixture will not be correct.

Jeez,you got to get those emissions under control Mitzy,..can cause you all sorts of problems,.....maybe if you try cutting back on the Spanish beer.

Whooops...!!!

Ok, strange ... I have a lambda sensor on my gearbox
Just going to have it put on a computer to check

You will have a reverse switch and maybe a speedo sensor but not a lambda/lander sensor on your gearbox.

Jon its "likely" to be a fault with the EPG / 02 sensor (as others have said) but check simple things first as Rotor has said ie vacum pipes / leads etc that may have been disturbed.
Think I read once (?) that if the fuel cap was not fitted properly on some cars it could cause this.

Of course the main dealers diagnostic tool should pinpoint it quickly & you could then order the part from the UK if you can wait for it to arrive & use the FTO meanwhile.

Oh well .... its just what the FTO parts dealer called it, as I need a new one

Been for the fault check and it bought up a speed sensor fault, however the machine re set it, and the emissions light has now gone out. He thinks it was to do with the battery being disconnected and said if it comes back on then it should go to a dealer

Yep , leaving the battery disconnected , particulary on late cars can result in a very big bill , ie grua to main agent , labour to reset the fault codes etc.