starting woes.

I have a 2002 freelander td4 2l diesel. Just before christmas during the brief snow in the uk, I arrived at work and the engine simply cut out with all warning lights on, had travelled 14 miles with no issues. Car has performed without any problems since June 2017. As the weather is cold and damp, am using 2nd car until weather improves before looking at landy.
A Mobile mechanic has suggested either a faulty Turbocharger or head gasket leak, potentially an arm and leg cost to repair only at a garage. Friends with landys have suggested the fuel pump inside the offside wheel arch may have a fault or filter blockage thus reducing fuel pressure. Snap-on EMS computer shows no fault codes.
Any thoughts / advice would be appreciated

You have posted on the LZ International 'RESCUE', which means that you have broken down somewhere and are potentially in trouble!
You really ought to go to the 'Introduce Yourself' and tell us that you are not a thief trying to nick someone's Gaylander, or post in the Gaylanderers forum.
I'm sure that @blue beasty will move this to the relevant place.

We must make allowances chaps. You can’t expect Freelander drivers to understand that a section entitled rescue means they require a rescue service.
They have so much more to worry about what with these new hair straighteners and the threat of a roadside butch test from the Village People Police.

Personally I would forget what the mobile mechanic as said, is the TD4 cranking over but just not firing, if it is cranking over maybe try a quick squirt of east start, see if it runs, if it does and cuts out do a leak back test on the injectors, if they look ok then check the wheel arch fuel pump and filter, you could also check the high pressure fuel pump regulator O-rings these are know to fail fix is £5.90 and about an hours work to remove the regulator change the O-rings, I/we await your reply before any other advice can be forth coming.

Don't know anything about Freelanders but I'd be testing the fuel pump is pushing fuel first.