fiesta tdci engine cuts out

[bodgit]

My daughters fiesta 1.4 tdci has started what she describes as losing power for a few seconds as if the engine cuts off. Its a 56 plate with 26000miles fully serviced but due one now. She,s done 9000 miles since she bought it in september mainly motorway driving 500 miles a week then local stuff. I drove it a few days ago and it seemed perfect.
I,ve booked it in for a service and diagnostic check but does anyone have any idea what it may be before I get told a b c from the dealer £££