Turbo part obsolete
Thanks to John I now have a nice new diaphragm for the recirculating dump valve. Unfortunately after speaking to several turbo specialists and suppliers, my search for a new wastegate actuator has shown that this part is now obsolete. I believe this is due to it being spot welded to it's bracket and having a relatively low rating of .4 to .5 bar, which relates to when the arm begins to move. So if you want to keep things standard and don't want to fit an adjustable aftermarket one like a Forge, your options are now limited.
One supplier has suggested if I remove the old actuator from the bracket they can supply a .3 bar rated stud fitted actuator which I can fit to the bracket, it could then have extra preload adjusted in to compensate for lower rating. At present I am going to try a decent secondhand standard actuator and see how it goes. The good news is that all the other parts for the turbo are still easily obtainable and I was quoted a price of £250+vat for a complete recon turbo of the shelf. I assume these companies must replace the actuator on a similar basis as suggested.