Is there anything else not working that may be the cause of the problem, like a seized blower fan motor overloading the circuit, what is the other problem you were working on.

It could be a short anywhere in the circuit after the fuse.

Are you looking for one of these. https://rimmerbros.com/Item--i-ASR1579

Try carrying out a fuel system purge/bleed before starting, if it starts ok then you will be getting air in the system, video link attached that may help.

50nm drain plug, 30nm fill plug.

My TD5 R380 gearbox has female plugs, a socket wrench fits the plug

We can only speculate but it could well be the servo diaphragm leaking.

Check the under bonnet alarm switch is straight and getting pressed down when bonnet closed.

https://workshop-manuals.com/landrover/defendertd5/electrical/under_seat_fuse_box_from_02my/

The injector harness may be letting oil back to the ECU under drivers seat, unplug and check the red socket on ECU for oil it is a common problem on TD5, and check for poor or dirty/corroded connections at fuel pump relay, check the fuel pressure regulator for leaks it is at rear drivers side...

Watch this video

Regularly go beating and the game keeper still has a TD5 110 pickup with Ifor Williams rigid cover to move the beaters around, he calls it the pig wagon, it should be called the sardine tin as you get crammed in like Sardines along with several dogs, great fun though.

I would not pay £50 postage for it.

What year is your TD5, it may not have had them on later models.

Look in the comments on this video for measurements

It is an alarm switch that sets off the alarm if the bonnet is opened while car is locked and alarm set, it is often the cause of spurious alarms if the switch is slightly bent to one side, ensure it is straight before closing bonnet.

https://www.google.com/search?client=tablet-android-samsung-nf-rev1&q=Land+Rover+paint+code+location&sa=X&ved=2ahUKEwiEtseh-9X8AhWSScAKHZRgC_0Q1QJ6BAhcEAE&biw=962&bih=601&dpr=1.33 https://www.lrworkshop.com/land-rover-paint-codes

That worked

Yes still will not allow me to upload, it says an error occurred, I do not have permission to view this page or perform this action, which is odd

Pressure regulator is on the drivers side of the block under inlet manifold, bulk end of block, Tried to attach photo and YouTube link but for some reason it is saying I am not Allowed, anyone else having this problem. ?