Hi Steve,
Thanks for the welcome, I wasn't advertised as having a steering fault (private sale) but I did drive it and although I thought it was heavy thought maybe it was just how it was. That appears not to be the case as I have since found out.
No untoward noises from the steering and the fluid is at max level, tyre pressures are okay. I've just took a gamble on the servotronic relay and bought another. Fingers crossed. If it's not that then it could be the module itself I suppose. Hoping it's not the rack/solenoid.
Thanks
Anthony