Thanks Vector,
I was worried that any of the replica parts bought from the States would be the eggshell consistency that I have in the roof now, although I was told by one UK parts supplier that the quality has improved over recent years. I am waiting for Plane Plastics to get back to me.
The problem I now seem to have is that the part that's there already is not the one that Piper list for my serial number. It would appear that whoever replaced the factory one last time ordered the part set that puts the vent knob in the rear duct rather than the console. It's not a major problem but it means either repeating the mistake or buying a whole roof set, front to back.
I am waiting on Paul Nalson getting back to me and then I will go with Plane Plastics if needs be.
If anyone knows of a lonely and unloved Warrier, Archer, Arrow or Dakota lurking at the back of a hangar do let me know.