Thanks for the advice. Is there anything distinctive about steering wheel vibration linked to the driveshafts? Do you suspect driveshafts due to the reason that from 40mph I can notice a vibrate? Any other major give aways?
Assuming you've checked for distorted wheels I'd have thought the next place to look would be the driveshafts and their joints. As the vibration is noticeable from such a low speed I'd check for the shafts running out of true and have a close look at the inner tripod joints.
And this will seem like a silly question but when looking at the driveshafts how can I tell if they are knackered or not?