Damp proofing single skinned walls reliable companies anyone?

[Chrysanthamum]

Me and my porch again,
I love it but its driving me nuts. We re-tiled the roof got brand new windows, had it replastered and we've been getting damp patches which are getting worse. we've tried sealant and I would now like to just get a specialist to sort it out before spending any more dosh or time on it. Its a great place for shoes, prams etc and has a lovely view & was one of the reasons I liked the house so much. Apparently Rentokil can deal with damp but I don't know anyone who has used them for damp proofing interior walls. I'd probably just bite the bullet and use them if I was confident that they'd sort out the problem, but I can't waste any more money. Also I live in a nice but nosey neighbourhood and don't want people thinking we have rats when they pull up outside!
Tips anyone?

Do not not NOT use Timberwise, would be my tip. Poor workmanship, expensive, hugely and disrespectfully messy, so much so that I'm still cleaning up a year later!

Whoever you use, it's likely to be a messy business and if you can be out of the way while it's going on I would. It could be that there is old saturated plaster behind the new plaster, in which case it will never dry out until you hack it all back.

Other than that I guess it's the usual advice about getting three or more quotes.

Where abouts are you? My husbands building company uses a company based in Oxford called Rentacure. I think they would do what you are asking.

Thanks kc3 but we're in central Scotland