I thought I'd have a go at the other (yellow) column mounting bolts today, I'll leave the bulkhead ones for now.
Took the bottom cowling off the column, nipped up the two yellow ones, tight, made very little difference, they were fairly tight anyway. I noticed while I had the cowl off that when I moved the wheel side to side (not turning) the whole of the tilt clamp was moving as I had it unclamped and between the clamp and the column were some laminated steel plates that separated as I moved the wheel. I believe it's these that are the wrong material (too soft) and are getting squished as any sideways force is put on the wheel.
Anyhow, because tightening this clamp nut too much makes it difficult to clamp or unclamp the tilt mechanism, what I did was set the wheel to my preferred tilt position, clamp it, then because I had easy access to the right hand (green) nut with the cowl off, I tightened the nut nut right up, foregoing the ability to adjust the wheel, and it's now solid, no play, no knock. We'll see how long that lasts, but for now I'm happy, I know exactly where the problem lies, I just can't know for sure why it loosens but I suspect rubbish materials on the clamp.
I can't see the point of having a new column if it's going to be the same a few months later.
Get bit of detective ?️

work
@Kithmo .
It will be interesting to hear, if increasing the pressure via the nut on the steering clamp, turns out to be a long term fix.
I like you, believe we have a couple of different issues causing this noise at the wheel.
The failed UJ in the video is more than a little concerning for both the owner and MG themselves that’s for sure !.
You would definitely be able to feel the play in the column, when rocking the steering wheel if the UJ was in this state.
There would be a considerable amount of free play present at the steering wheel, that’s for sure !.
A couple of U.K. owners have had there columns replaced, which had cured the problem it would appear.
MG must be 100% aware of this issue, because they have released a service bulletin ( MG - 0020 ) that recognises the problem.
I understand, this MG - SB recommends replacing the steering column, not sure if this means the entire column assembly, or just the lower section, that houses both of the UJ joints, I have no idea.
This section is splined to the column at the upper point and the lower point attaches to a similar splined shaft of the steering rack.
Both points have a pinch bolt that passes through the knuckles of the coupling and is then torqued up to the manufactures spec.
MG would not be taking this type of action unless they where total convinced that it was a real safety concern.
Maybe they have identified a problem with the UJ joints, on certain cars that has resulted in premature failure.
UJ steering joints are see a potential wear point, but certainly NOT at this early stage in the cars life !.