An update on the above:
Booked an appointment with a local gearbox specialist - earliest I could get is 22/03/24.
Took the car to get some fuel last weekend, and it was driving OK below 30mph but still making the noise above 30mph.
No lights on the dash, no warnings etc.
Above 30mph the car felt like it was juddering and when taking my foot off the brake (its automatic) the car was slowing down a lot more than it should be.
Turns out the front right brake had ceased again (was extremely hot after the short drive) - so I had 4 new discs fitted, and pads all round, and replaced the front right calliper.
The noise was still evident - I thought if the brake calliper had been intermittently failing with unnoticeable signs, this may have stressed out the new wheel bearing I fitted in October.
Jacked the car up - no play in the wheel
Took the hub bolt out - no play in the wheel
Took the wheel and calliper off - no play when trying to wobble the disk
Took the wheel bearing hub assembly off (4 bolts at the back) and inspected the bearing, this identified a lot of play, and grease leaking out the seals.
Changed the bearing again, and the noise has now completely gone 😃
I do have another problem now though, which I'm not sure whether it's due to the above or not - possibly!
There is a rattle coming from what I've investigated to be under the transmission bell housing.
The rattle is evident when idle, in neutral, in drive/reverse but only when the brake pedal is pressed (auto). Once the brake is released and car starts moving, the rattle goes.
I'd suspect this is the dual mass flywheel - I'm going to keep my diagnostic appointment on the 22nd and get it 100% confirmed.