IMHO, for what its worth, you`d be mad not to take up the chance of getting A/D + APP. You`ll increase your chances of getting to work in your own part of the country and should you ever get fed up with Nats or vice versa you`ll be able to get other A/D work whereas if it doesn`t work out on the area side you`re gonna struggle.
Besides there`s a pretty good chance you`d be able to transfer from Airport to Centre work at a later stage as the staff shortages are only gonna get worse. What are the chances now of Nats letting a valid area controller go the other way.
Having seen both sides of it first hand, albeit not as a valid area controller, the chance of ending up working south of Manch with no escape would be enough to make me do A/D.