Cadbury only disappeared from the park as Merlin signed a deal with Nestle. Now that Cadbury are back as sponsors/suppliers, I can't imagine why cross-promotion wouldn't begin again, nor can I see why Mondolez would be unwilling to hawk the brand wherever and as visibly as possible?
Undoubtedly owing to my nineties childhood visiting the park and the anticipation of a visit to the Chocolate House, but Cadbury always felt right for Alton Towers, in a way that Nestle didn't. Although, hardly a dealbreaker in the grand scheme of things.