Credit card balance transfers question

[Hackney]

If I have a £5,000 credit card balance and £3,000 of that is made up of a 0% offer and the remaining £2,000 is interest bearing any payments I make are taken from the interest bearing part of the balance first.

But what if I want to transfer some of this balance to another 0% offer, presumably the same principle would apply? Interest bearing balance is transferred?

[otolith]

As I understand it, it is mandatory to pay down the highest interest bearing balance first. It shouldn't make any difference where the money comes from.