Hi LouR,
Just wanted to chime in with some 'advice' as requested by you - but, please, keep in mind that I am in no position to be taken seriously... I am 3-and-a-half years since BD, now D-ed, and with no sign of XH being anything other than increasingly nasty and punitive.

So, that being said!, here's the benefit of my experience:

Nothing that you do or say will have much effect on your H. Other than that if you continue to try for R talk and contact with him, he will pull away even further.

In my case, XH is a controller and so is always telling me what I should do - in relation to finances and kids - so when I don't do what he says, I can be pretty certain that some sort of retaliation will follow.

You seem to know already what you need to do:
"I know I need to stand back and allow him to work though his own journey and I need to keep moving forward on mine."

This sounds like the best plan. As others have said, do what feels right for you and your boys.

You cannot expect anything from this man. Remember: he was the one you thought you could depend on for ever. He is not that man any more and, in this sense, you don't know him at all, and hence cannot have any expectations.

I really connected with your story - I heard exactly the same words at BD: "I can't do this anymore. I want my freedom".

And then he went off like a kid in a candy store, spending wildly and living it up with OW, completely without care for what our kids (12 and 15 at the time) thought or felt.
Nothing much has changed for him after 3 years....He still appears to have it all and we continue to feel the unfairness.

But we also feel better off without him in so many ways, and we have learnt to be better people.

I am in Aus and felt a kind of connectedness to see that you're living in NZ.

Try to enjoy your trip back to the UK - the idea of returning to be close to your sons sounds like a good idea to me - even big kids need their mum! In any case, you can go with the flow now that you're not so tied down and have the opportunity to try out so many new things.

Best, NLW.