Damp issue/Paint peeling....tiling?

[robodelfy]

I recently renovated my kitchen. I put a mist coat on the bare plaster that was behind the kitchen cabinets and tiles. In the last few weeks it has started peeling off in a small area. The rest seems fine.

This wall is between me and my neighbours house. I did have a bit of damp in the corner of this room, but I'm almost certain this is due to an external wall that is tied in to the house outside and gets soaking wet. I will be knocking down this wall and rendering where it joins. I wonder if this new peeling paint issue could be relate to that too.

Any advice? I want to tile over this area, so I was stupid to mist coated it at all. The last tiles were on for 20 years and seemed solid, so is it an issue if this paint peels a bit? Could I just tile over it all

Thanks