Fueling Issues - Disco 1

I have a 1991, 200tdi H reg discovery 1. the car has completed 215 500 miles. its not a regularily every day go to work car, but used for greenlaning and most weekends to get the fluids running.
Over the last couple of months the car has had issues with fueling issues. It has often refused to start even when there is a full tank of diesel, and the battery is fully charged. It has had a diesel cut off solenoid (replaced 2.5months ago), and last month the diesel lift pump was replaced along with a new fuel filter when the vehicle refused to start again. the same symptons have re-appeared again. the vehicle lights up like usual, tries to tun over but doesn`t fire up. any ideas?
When the garage replaced the lift pump & fuel filter they remarked that the filter was full of crsp (the vehicle had had a service last october with filter change last november for the MOT asn had only done 3500 miles since this failure).
Any ideas what might be know wrong with it? The vehicle has a full tank of diesel.
Thanks

has the sediment bowl been cleaned out?

I presume this is the one located under the car located near the fuel tank?

I can only presume that the garage looked at it (or possibly not), as i'm a novice mechanic i haven`t. is it an easy job to do or is wise to leave it with someone that knows? last thing i want so 75litres of diesel flooding the driveway!

Back to basics, and logic.

Engine won't start.

Question: Is fuel at high pressure reaching the injectors?

Way to find out: slacken on or more injectors pipes at trhe injector(s) end, and turn engine over. After a few turns, it either drips / squirts fuel, in little spurts, or not.

Once you have done this, and reported back, we can go a step further.

CharlesY