Thanks for the replies everyone.
My neck issue is a tighten of my neck and Lat muscles caused by shoulder misalignment and a slight scoliosis. Essentially when in the road position, my body is trying to pull my neck up and left which results in inflammation and pain.
At its worst on a long 4-5hr rides I end with I can’t turn my head to the left. I have regular physio, and actually it was doing well until I took out my “good” bike last weekend over two days and it flared up.
I’ve had bike fits, and do stretches but if feels like I need to call time on anything other than a relaxed geo. I’m about to go out for 3hrs now and yesterday rotated my bars a little to bring the hoods closer as a last resort.