No recommendation but a bit of advice.
We thought we had some damp on an internal wall and asked two companies to diagnose and quote. Both said that it was probably rising damp and quoted about £750 for the work. I did a bit of research and discovered that rising damp is notoriously fabricated problem wuth rogue tradesman and that some people believe there is even no such thing (I forget the details but spend half an hour on google).
In short, our decorator removed the (waterproof) wallpaper that had bubbled and become discoloured, to reveal perfect plaster and a diagnosis of condensation.
We were so close to commissioning one of the aforementioned companies, especially when they offered us a last minute cancellation at a reduced price.
I'm not saying you don't have it, just advising you to do sone homework