The fuel injector light started to come on and off the car and then some weeks later a noticable drop in performance. My local back street garage replaced the ecu/fuel air meter thingy (sorry about mechanical expertise) for about £250 and the car came good again. That was 3 months ago and the injector light came back on intermitently last week and now the car is sluggish again.

Can the ecu thingy break within a short period or is there another cause of the problem??:

i seriously doubt they changed the ecu for £250. a new ecu alone would cost more than that, and a used one wouldnt work with your car. did you actually see a new ecu get fitted? have you since checked to see if it was changed?

changing the MAF or MAP sounds more likely what they did, thats often a cause of these problems on the diesel. maybe the new one is now dead. if you know for definate which sensor they changed you could try changing it again with one from a scrapyard (£5max). if that doesnt work get a fiat diagnostic check done, they do it best. when they tell you whats wrong fix it yourself, or get it fixed elsewhere, to save money.

If they used a MAF from Ebay it'll more than likely be duff by now. Get a genuine one from either Andrew Page, shop4parts. Its about £150. Takes 5mins to fit.