2005 C-Max Engine Wont Start

Hi,

I have a 2005, 2 ltr TDCI Focus C-Max, 46k miles.
About 2 weeks ago the car wouldn't start, my wife left it for 15 mins tried it again and it started. The car was fine until this week.
The car wont start, the battery and starter motor are new and are fine. I had a diagnostic check and the chap said it was showing a cam belt sensor fault.

He changed the cam belt sensor, tried to start up the car, only for the same fault to come back. The engine attempts to get started but cant even turnover. The chap doing the diagnostic check was puzzled and said he thinks the cam belt has moved which has caused damage to the engine.
Best case it would be a costly repair job on the existing engine (£800-1000 min) or worst case the engine would need to be replaced, which is obviously very expensive.

Has anyone had a similar problems or other thoughts what the issue could be?
Does the information I have been given sound accurate?

Anyone know any good garages in north hertfordshire (I live in Letchworth, near Stevenage) that would do a good job with this sort of work?

We only brought the car about 7 months ago with a 6 month warranty, despite the cars age I thought I had a good deal as I thought cam belts needed to be changed at about 60k miles. The chap that checked the engine for me said its based on age as well as milage and the car is coming up to the point were the cam belt needed to be changed. Is this correct? Is it something the garage should have done before selling the car?
I'm gutted brought the car for £3800, love the car so don't want to get rid of it but seem to have limited choices.

Any help or advice is appreciated