Straight off i know nothing about diagnostics, and i'm not convinced it's anything to do with engine management, common theme that gets this car going each time is a new filter...or rather a filter full of fuel.

Have you owned this car long? If you have did you try to use any bio fuel or veg oil in the tank, if it's recent purchase i'd first be looking at something fuel related, maybe previous misfuel.

My first action would be to buy a new fuel filter, keep it with you and learn how to change it.

Does the car have a primer pump, being a Ford i doubt it, keep a bottle of ''clean'' fuel in the boot anyway, put it in the tank and refill regularly with fresh fuel if you don't need it for the following.

If the car breaks down again, remove the existing fuel filter at the roadside...is it full of fuel?, no?, then top this filter up with clean fuel, offer it up and continue. If it's full of fuel, fill your new one with clean fuel, fit and continue.

This should reveal whether you have a fuel starvation problem or filthy fuel problem, then you can investigate further.

If it's muck then i'd remove the tank and clean it properly, and after disconnecting blow through the fuel lines with compressed air.

If it's fuel starvation you might be better off going to a Diesel specialists instead of the main dealer, i'd be doing that anyway.

If fuel starvation is the problem perhaps it be worth checking the operation of the lift pump which supplies fuel to the high-presure diesel pump? Could be the lift pump is weak or has an intermittent electrical fault, or else has a blocked filter?

If that's OK then perhaps the high-pressure pump could be suspect? There was an early problem with these engines in that the high pressure pumps would wear out and fill the fuel system with metallic wear particles. I'd have thought these issues would have been resolved by now although I suppose it's still possible the pumps could be wearing out due to old age or the use of incorrect fuel (e.g: excessive biodiesel blends or veg oil). The HP pump relies on the lubricating properties of the diesel fuel and Ford do not recommend using more than 5% biodiesel.

The diagnostic may he highlighting a rail pressure problem but the cause may not be a faulty switch. The pressure can only be attained if sufficient fuel is being supplied ( blocked filter, faulty low pressure tank pump, air in the fuel ), or because pressure is being lost ( faulty high pressure pump, leaking injector, faulty pressure regulator).

I would take it to a diesel specialist or you could be throwing good money after bad.

No, the diagnostic code just tells you what the problem is ie low fuel rail pressure, not what is causing it. See my post above for possible causes.