Help needed20

I think I may have found the issue , neighbour has a raised flower bed which is directly on the corner I have the issue .

Radiator wall is external , further investigation has found no dpc in affected are , I believe there is multiple culprits here

Just started getting plaster off , the bonding coat is so thick , is this normal ?

When I get home ill post more pics etc , I shall be taking plaster off today as a day off

Exterior wall with the vent is a cavity wall , concrete floor , room is extended kitchen, heating goes on no clothes put in this area , no downpipes or anything with leaks

Just a hole in wall with vent cover either side , wall outside is in good condition

Have this damp in room and noticed the wall vent has no ducting going through it any advice ?