Need HELP

Can any 1 help i have had the engine management light come on with message anti pollution fault/unblock diesel filter and it also feels the car has gone into a limp mode as it struggles to go beyond 2500 revs it also still runs on 4 a few seconds after turning the engine off.

I have had a pug mechanic connect it to his computer and he said its the high pressure pump it has broken up and there is swarf in the system told me it would need a new 1 along with new injectors and the engine flushed at a cost of £900 as any 1 had the same problem or can any1 throw any ideas my way