[Laird Scooby]

If someone has played with the throttle stop screw the idle could be too high now. However that or even an AICV fault won't cause the problem you're getting.

Have you tried dead-ending the fuel line to bring the pressure up? If you have a hydraulic hose clamp (like you use on a brake flexi hose when changing a caliper for example) fit it on the return hose from the fuel pressure regulator (FPR) and clamp it to bring the pressure up. If it then revs happily, it would point to a dodgy FPR as well.
If you don't have a hydraulic hose clamp, two smooth handled spanners with the handles crossed, one either side of the hose and then clamped with a pair of Mole grips will do the job.

There should also be a vacuum hose on the FPR, check this is intact and secure and also that the manifold stuib it goes onto is clear and not blocked.
If you pull the vac hose off the FPR with it idling and put your thumb over the end of the hose, wait and watch for fuel coming out of the stub on the FPR - shouldn't happen.

The big thing now is nobody knows when this problem started, whether it came on gradually or suddenly so we're shooting in the dark somewhat. I'd check the cam belt timing first as that's pretty likely then work through the other things, probably next would be to check the feed on the underbody pump (could be corroded terminals that just need cleaning) then the FPR to see if you can find any clues as to what's causing the problem. Might be several problems there.