Bob wrote:
I have a wall that was damp and caused contaminated plaster (i.e salts)

Traditionally, the reccomended solution is to replaster (using Thistle
Driwall). However I can considering replacing with plasterboard?

What type of plasterboard should I be using? I have googled and found
mention of "damp proof" plasterboard, but when looking at the travis perkins
website, the range become confusing? Is Gyproc Moisture Resistant the stuff?
or should I be using something else? (i.e plaster with driwall, or other
plasterboard?)

Moisture resistant plasterboard is moisture resistant, it will not stand
constant damp.

If you have constant damp, you need to fix it.