This isn't really answering your question but we had the same problem with condensation on external walls even with dehumidifier running.
And while we looked at drylining or external insulation, financially it wasn't workable for us. We've used this product.
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while not tackling the root cause of the condensation it did at least stop it from forming on the bedroom walls and I think warmed up the room a little too.
But of course if you are able to get the root problem sorted that would be the best option.