severe vibration

hi there , i had my landrover freelander in garage to replace ird unit ,i also had the centre bearings and the rear diff mountings done and new front prop, since i got the car back its gained a severe vibration or shudder when going over 30 mph the gear lever also moves(shudders) iv had it back to the garage and he said it was a defective joint on the front prop and replaced under warranty, iv drove the car today and the shudering has started again but worse any ideas guys as im at witts end with the car having already spent £2000. any ideas what this could be thanks.

could it be something as simple as if theyve removed all 4 wheels to do the work the rears have ended up on the front and the front on the rear and the balancings out?

or wheel bearings?
or ujs?

when i drive the car on snow where it hasnt got grip it drives fine ,but on main roads which are clear the shuddering starts again? any ideas please?