Noisy head

Hi there,
I wonder if any of you chaps have any ideas to help, me with a very "sick" sounding td5. There is rather a lot of noise coming from the cylinder head. Sounds that are reminiscent of badly ajusted tappets on a side valve engine. Now at some time before my ownership the cylinder head gasket was replaced by a team of monkeys to judge by the "collateral" damage; bolts holding turbo switch missing, broken engine cutout switch and damage to the sound proofing on the bulkhead, just to give you a flavour. In the light of this I'm wondering whether A, the adjustment on the injector rockers was done correctly and B whether the hydrologic tappets were primed?
Now to set about correcting this; to reset the injector rocker stroke, can this be done with fuel still in the injectors or should I run it out of fuel first. Can I run it out by just removing the fuel pump fuse?
I should add that the car is very down on power but I suspect that this maybe a turbo issue.
Any thoughs on this would be very gratefully received.
All the best
Mac.

Hi Has it always made this noise? Oil level ok? When was the oil last changed?
The hydraulic lash adjusters have very small holes in them so if the oil is mucky they may not be working properly.
Yes do the adjustment on the injector plungers asap!

Thanks for coming back to me, so promptly, Mark. I bought the car rather in haste as my other Discovery TD5 would have failed the mot on chassis rot. So I do have the two cars together to compare. I've had the 04 model just over a month. I did a full oil change within about a month of getting it, oil filter, centrifuge and fuel filter. The engine was always a little noisy with what sounded like a tappet but It does seem to be getting worse. There are also some strange sounds coming from the exhust, I did wonder if that could be the fuel pump though or can one hear the turbo?
Again thanks for your reply. Should I reset the injectors dry or with fuel?

injector clearance is set with injectors fitted you turn engine till injector is fully depressed, slacken locknut ,adjust till back lash is removed and then unscrew one full turn lock locknut move on to the next, warped manifolds and so blowing gaskets are common,its worth checking crank pulley/damper they can cause a knock