Original poster wrote replastered (green board). Just assuming the room has been skimmed if I’m wrong then I hold my hands up, but they also mentioned the room only being part tiled so again an assumption that it had been skimmed for decoration.
Hi- yes, sorry if I wasn't clear. The room was reboarded and then skimmed THEN I stupidly gave it a coat of paint.
Look, you've made a bit of a twit of yourself on your first post, it happens. Move on, learn, and be a productive member of the forum.
Despite differing views on here, you won't have a problem provided the plasterboard was screwed on securely in the first place. Don't worry about the mist coat, it's purpose is to sink in and seal, not provide a key for the tiles to adhere to, just carry on.
I’m afraid I can’t agree with that comment, British Standards state that tiling onto a painted substrate is not recommended, there is not a single adhesive manufacturer that will recommend this either, original poster is using Mapei adhesive, give their technical line a call and see what they say. I know the answer they will give you.