[Engine] replacing diesel fuel pipe

[Harry-A]

2004 1.9d Berlingo cold starting problem well covered here, but mine is a little different.  I know it'll start eventually, (just before you think, "the battery, or the starter motor canna take anymore captain). It really does take ages to get going from cold, so anything I can do to help it has to be worth trying, so here's the problem. Somewhere along the way, a previous owner has fitted, what I believe to be , a one way valve in the tubing from the metal feed pipe from the diesel tank to the fuel filter, ie before the pump.
I'm wondering wether such valve could be clogged with detritus from the tank, making the initial starting fuel feed, um, not as good as it could be, like without said valve in the line. (It's before the  diesel filter?) The plastic tubing from the metal tank pipe, with the strange metal "one way valve?" is a hard plastic that seems to be heat shrunk on to the connectors, and the simplest way I can think to replace it would be to cut away the hard plastic stuff, complete with strange valve and use the rubbery stuff you can buy in auto supply places, to be held in place with jubilee type clips, (without the valve thing, of course) Or do diesels have to use the stuff that's on it now?