L322 td6 high pressure pump gone(i think)

soooo, here we go again another day another problem,

started noticing small amounts of diesel dripping from the front end and the td6 hesitating in the higher rev range, then it wouldnt rev over 3k at all, twice in two days it has failed to start after these issues, strangely if i left it a while it would fire up and drive no issues,
but then today after it passed the mot, it broke down cut out driving up hill, fuel pressure pump alarm on the dash,
so i check the lines under the bonnet and ive got fuel coming through but can see alot of wetness on top of the hp fuel pump, step dad gave it a whack while i cranked it and it splutterd into life drive home faultless,
scratching my head now because it doesnt seem a straigthforward replacement and bloody expensive (£650 +vat for the part)
any tips to look for before ordering everything and stripping it down

Do the 'Wheeler Dealers' test....

Pull an injector out and place in a jar, connect the diesel line and the wiring harness to it and crank the engine...the spray pattern should be even, strong and fine, test each injector in turn....if any of them are a little lacking, it may be the HP pump is weak or that particular injector needs a refurb!

cheers saint ill give it a go, but still leaves me with the headache of getting the pump out at that cost