Bad vibration type noise ?

Strange one this, just taken the motor for a quick spin as I tend to do when it`s cold.
Car was fine yesterday, no problems what so ever. But today as I got up to 45mph a horrible vibration/out of balance type noise started, that`s about the best I can describe it. There was no vibration through the steering, but at 50mph it was unbearable so I quickly reduced speed to prevent any possible damage to whatever it may be.
Back on the drive at home I clambered under and checked all drive/propshafts for abnormal movement, all ok, but noticed huge clumps of ice clinging to everything.
Once de-iced I took the car for a test and all ok once again.
So all I can presume was that it was a build up of ice causing something to run out of balance.

Anyone had anything similar?

Yep. Once had mud doing the same thing after going to a pay and play day. Seemed to be sitting in a clump on the inner edge of a wheel. Amazing what a difference it can make to how the car feels when driving.

Started to happen again today on the way to work, so when I got home (approx 5pm) grabbed the torch and looked under.
And I was amazed at the amount of ice stuck on the N/S/R drive shaft, must have been throwing it out of balance by one hell of an amount.
Chipped it all off and went for a test drive, all back to normal again.
Just something to keep my eye on in this weather.

Thought I had solved the problem but apparently not. The noise is back but now from 60+ mph and is unbearable by 70. Anyone any ideas as to what the problem might be?

Don't know. Perhaps kift the rear wheels and turn then to see if buckled. Then same on the front.

Has the ice knocked off your balance weights. (There are some on the inside of the wheels as well as outside).

After having a thorough de-icing session she seems to be running normal again. The build up of ice on both the N/S and O/S lower front suspension members must have been a good 4 inch thick and weighed a good couple of pounds each side.
There were also a few chunks of ice (a couple of ounces a piece at least) stuck to the inside of each front wheel rim and I know for a fact that even that small amount would have put the wheels well out of balance.
Just have to keep an eye out for any more build ups of ice!