These things usually leak fuel, which dribbles down the back of the engine, onto the bellhousing, and onto the ground. If you have a fuel leak from this area, you can get under the vehicle and look upwards to check where the leak is coming from. Replacing the regulator is very difficult - it's held to the rear lower corner of the cylinder head by 3 x 10mm head bolts. The engine cover, rear lifting eye, heater pipes, and inlet manifold are all in the way.
There are two types of regulator - EU3 models (3-pipe connections), and pre-EU3 models (2-pipe connections). This is the three-pipe type.
Access can be made a lot easier by removing the inlet manifold, and if you have big hands, then you may have to. Removing the manifold is by no means easy either, and I have left it in place in this thread.
This is the pressure regulator (about £90) - the diaphragm at the rear is what leaks and it's held to the regulator housing by a circlip, but you have to buy the whole thing - including the top pipe, which you don't actually need.
You'll be reaching over the engine on the drivers side, so a box/spare wheel/etc to stand on will save your ribs.
Remove the engine cover - 2 x 13mm bolts on the passenger side, and one on the drivers side.
You will now be able to see the regulator - very awkward/tight position.
The fuel cooler is held to the inlet manifold by 4 x 10mm head bolts, remove them and the cooler will come loose. Disconnect the top fuel line by pushing the black shroud to the left and the pipe will slide off. There'll be a very small amount of fuel loss.
The heater hose nearest to the head next. Compress the clip with a pair of mole grips or pliers, slide it onto the pipe, and then carefully remove the pipe - taking care not to damage the heater matrix pipework. There will be a small amount of coolant loss, but not much. Tuck the pipe forwards alongside the inlet manifold and keep the end high to prevent any more coolant from draining out. Unclip the gearbox breather pipe and tuck it behind the head out of the way.
The engine lifting eye is secured by 2 x 10mm head bolts. Remove them and the eye.
Getting there !
Top pipe next - you get a new one, but it's not necessary to use it. If you do, then there's more work involved to disconnect the other end of it at the front of the engine. 14mm spanner to undo it - slide the nut up the pipe, spray some WD40 in the hole to lubricate the small O-ring seal, and the pipe will come out with a sharp tug.
Disconnect the sensor by pressing the metal clip inwards and sliding the plug off.
The three bolts that hold the regulator to the head now. Bottom one first, which is very awkward to get at. You will have to reach under the inlet manifold to get the 10mm socket on and make sure you get the right bolt - one of the inlet manifold bolts is right next to it.
Remove the other two bolts and the regulator will come away (there's a shim steel gasket as well, so recover it)
The middle pipe connection has a clip fitting, but it's difficult to get at, so unscrew the pipe with a 14mm spanner instead for now. The bottom pipe is the one you disconnected from the cooler, so no need to undo it.
Once the regulator is off, unclip the pipe from the stub (squeeze the two square tabs in and slide it off), which you won't be using.
Put the new regulator on - top bolts first and don't forget the gasket. Clip the pipe on the new stub, reattach the top pipe, then bolt the cooler back in place and connect the final pipe.
The old regulator - the clean area indicates where the leak was coming from.
Replace the lifting eye and reconnect the heater pipe, but leave the engine top cover off for now.
Turn the ignition on and let the system self-bleed. You will hear squishing/squirting noises from the filter/fuel tank as it does this. Once the pump has stopped, start the engine and check for leaks from any of the pipe connections. They make am audible click when they are fitted, so leaks are very unlikely. Once you are happy that all is ok, replace the engine top cover and close the bonnet.