So Apple is non-compliant, given that all they did is disable ADP in the UK.

Right?

I think that's right, and I think the UK will tell them so, and the issue will escalate.

Perhaps, if the UK continues to push, Apple will indeed pull out of the UK, but it'll make it as public as possible and tell the world who it was that forced its hand and what the consequences are - and I don't think the UK government is going to like that result.

IANAL but that's not for any of us to decide. Depending on their initial motivations, the UK might consider this to be enough to rescind the demand for a backdoor. If it's not then Apple will face going to court and in that case they could choose more extreme actions like ceasing business in the UK.

they're non-complient but they made it a lot harder for the UK to fight. by showing that the "backdoor" is disabling the feature, for the UK to pursue this further, the need a judge to rule that the UK has the authority to prevent an American company from providing a feature in America.