Damp in cupboard- insulation problem?

[Twoshoesnewshoes]

We have a cupboard which is the old front porch.

it’s always been very cold - I think built just one brick thick and no proper flooring.
we keep coats in there and it smells musty.
so a couple of years ago, we lined the whole cupboard internally with rockwool insulation, and painted over this.

in the past few months, the cupboard has smelled really damp. I can smell it through the house. I’ve put a dehumidifier in there (the humidity was 70), but I’m wondering if I need to take the insulation off? Has this just trapped the damp against the wall?

Perhaps I should have added a heater instead?

Bricks are porous and with the amount of rain it could be that rain is permeating the walls. You can seal bricks externally and that might help. It might also be beneficial to take off the insulation, as it is possibly soaked through and trapping the damp. Best to have a look and a small hole will let you know if the insulation is wet.

Yes that’s a good idea
the house is rendered but it probably has small cracks in, and is starting to lift in places.
oh no
do I need the house re- rendering?