UK does not pay.
The EU is likely to develop a military at some point and has some defence cooperation. if you do not trust the US, that means you cannot rely on NATO, which means you need some alternative.
> Right now it seems to me that e. g. Carney, and Leyen, use this more as promo-tour.
I agree. It might be meant as a threat to influence US policy.
That could be a european Nato though, doesn't mean you need literally one EU army