Hi Stuart,
Firstly, great tree - I have a similar one to this as well. Your wiring also looks really neat!!
I have attached a photo below to show what I would do this tree.
A)I would chop this section of the tree back to the branch I've circled B and make it the new leader. The reaons are ;
1-The tree needs some better taper. It will also be easier to put subtle movement in the thinner branches.
2- As you go higher up the tree, the distance between the branches should decrease, in your tree there is a substantial blank piece of trunk between the part I've labelled B and the next branch up.
C) This first branch is way to thick in my opinion, it looks as though it's almost 70% the thickness of the trunk,it's movement looks very unnatural and is going to be difficult to correct IMO. I would chop this back and create a jin out of it.
In terms of repotting, I would say MID winter (July) would be the best time.
That's what I would do it it were my tree. Others may completely disagree with me or have alternative ideas.