I have a pretty severe clunking noise when driving over potholes and drain covers, so I had a look at the offending side.
The top mount/bearing has a heck of alot of play in it, so replacement is on the cards.
My question is, is it likely to be the bearing, the rubber top hat or both that are bad?

 

If the strut nut springs back after turning it, the spring rubber still good. If you can turn the nut and it stays, the spring rubber is bad. That can make the clunking sound. I am not sure if the bearing plate will make the same sound, if any, once it goes bad. Take a look at the sway bar end links too. If they have play they can knock.

 

The rubber was goosed!!
Replacement was cheap and easy and now my car doesn't make a noise..Reeeesult.

 

Which part making the noise did you replace..........not sure from your description........the upper motor mount?

 

No, the upper front spring mount. The centre of it, the bit that the threaded part of the strut passes through, had become completely detached.