Hello there! I don't really know where to start so I'll give you a short version and a long version...

The short version:
Will the pressure regulator valve off a 0 445 010 010 Bosch fuel pump fit a 0 445 010 046 pump?
I know the pumps are both CP1 and are interchangeable but are the pressure regulator valves also interchangeable between pumps?

The long version:
I have a 2001 406 with 350,000 miles on it. Its a 2.0 HDi (90bhp) and has been a great car to us over the years.
A few weeks ago the engine light came on and it started running on for a second or 2 after it was turned off at the ignition.
Then after a few days, there was some power loss (difficult to say how much because i never really push the car too hard anyway).
About a week after that, the engine cut out when I was slowing down on the motorway.
Since then it has been cutting out intermittently when I'm slowing down - especially when I'm going down through the gears. Usually it doesn't cut out until its warm, but sometimes it does. It also cut out while idling at traffic lights once when cold (this was the only time it cut out when idling but not the only time when it cut out while cold).

The fuel filter was changed a few thousand miles ago so I know that that's not the problem.
I took it to a friend who ran it through his diagnostics and cleared a few codes but the one that seems to be causing the problem is the "Pressure Regulator Valve" (I don't know what the code number was).
I know that the pressure regulator valve is on the back of the fuel pump but I can't seem to find one for my pump at a decent price in Northern Ireland.
A new Bosch regulator for my pump is £180 and a new non-Bosch regulator is £115 but I don't want to pay that sort of cash for something that might not solve the problem.
The part number for my pump is 0 445 010 046 and the part number for my pressure regulator valve is 0281 002 493 but nobody about here seems to be selling the same pump as mine and I don't know if the pressure regulator off the other Bosch pump (part number: 0 445 010 010) is the same as mine.
I have been offered 3 or 4 of those (0445010010 complete pump) at £40 or £50 and I'm told that its ok to replace the 046 pump with the 010 pump but I don't want to pay someone to change the pump until it needs to be changed (the timing belt was changed about 30 or 40,000 miles ago so its not even worth it in that sense).

So... Will the pressure regulator valve off a 0445010010 fit the 0445010046 or do I need to replace the whole pump?
Or maybe my friend is wrong and the pressure regulator valve isn't the problem?