I fitted the Pagid discs, brake sensor and pads, the juddering has gone, phew!
Strangely though, the offside disc had been fitted, WITHOUT the two retaining screw, they had been sheared off! The car has a full service history, I have have found a receipt for the disc and their fitting from two years ago by a motor engineer company in Glasgow, to be honest, I'm appalled that a reputable company should have done such a shoddy repair. I have drilled the studs out and recut the threads, it took me about half an hour, this is exactly why I now do all my own repairs and servicing (with help and guidance from my brother, a trained Jaguar engineer) you seemingly can't trust anyone?