Ford Mondeo loss of power and glow plug indicator light flashing after brief engine stutter.

Engine stuttered on approach to roundabout and glow plug indicator light started flashing. Had decelerated smoothly from 70MPH in 6th to around 35MPH in 3rd and was about to accelerate onto the roundabout when the brief stutter occured. Following the initial brief stutter, engine went back to running smooth, but with noticeable loss in power. Engine remained this way (smooth, but very much underpowered running) with glow plug warning light still flashing for rest of journey (gently cruised it the remaining 25miles home).

Cam belt sensor recently failed and was replaced immediately prior to last service, which was carried out a month (~2400miles) ago. Have experienced the odd very brief engine stutter - no associated warning lights or loss of engine performance - when cruising at motorway speeds on a couple of occasions since service over last month. No other engine faults in the 2yrs-9mths (and 47,000 miles I've owned it). Car has now done 98,000 (mainly low stress motorway cruising) miles.

Owners manual does not provide any detail on this indicator light flashing during running.

Don't think this has anything to do with it, but......have been running on Shell V-Power Diesel (had just put in 5th tank-full since recent service when the fault described above occured). As a side note, was giving this a try as bonus Shell points over Sept and Oct made it worth a go - have noticed absolutely no improvement in economy (mpg) over standard diesel. Although did convince myself that engine seemed ever so slightly more responsive.