07 TDCi grinding noise

[Skwirls]

Hi folks, I bought a Focus tdci a couple of months ago, only ever had Jap cars so everything is foreign to me now. Anyway, twice recently its briefly made this awful sound exactly like you've tried to start it when it's already going, like the starter is engaging while driving. First time I was just putting around in 1st in the supermarket carpark, yesterday I was doing 60kph in 4th, it lasts for a second or so. It sounds like its coming from the rear of the engine down low, comes through the firewall down near the clutch pedal?