-
What is the issue with getting to the outside of the wall? The only real answer is to stop the water getting into the wall in the first place. If you can’t dig up next door the get a gully in and tank the wall, how about just digging a slit trench along the wall and pouring in tanking slurry? If they won’t let you do that drill a load of holes straight through the wall and pump slurry into the gound from your side. Get enough in and it should stop the water.
I think an airbrick is akin to pissing in the wind. A fan is better. Dehumidifier a lot cheaper than all your plans.