Just to "chuck" my ha'penny worth into the ring. I have bought a number of parts (metal coolant pipe etc) and service items (oil etc) from Shop4parts. and found them to be of good quality. Other than that I mostly buy from my local factor (SRS). I find Mike at S4p very helpful and it's well worth just giving him a quick ring about anything you're unsure on.
I agree with our moderator on the clutch hydraulics. I've had problems with this on both our own 1.2 Panda and my boy's 1.4 8 valve Punto - still sorting out the Punto and it's looking like both slave and master cylinders are going to be needed. I'll probably buy from S4p.