There were two Whatman's papers available about five years ago that were fantastic for pt/pd. One was Whatman's Printmaker and the other was Whatman's Watercolor, both of them hot press versions. New York Central Art Supply carried them for a while, and then they were available for a while through Ken Bromley in the UK.
The papers were were pretty similar. Both were slightly buffered, and turned out killer prints on pure pd if treated in a five minute 1-2% oxalic. They were both sized with Aquapel, which made them work really well as pure platinum papers. The tone in pure Pd was warm, but not quite as warm as Platine developed in really potassium oxalate.
Both papers had the other wonderful feature of being dimensionally stable - that is - they were great for multiple printing and you would not run into weird registration problems when doing gum over platinum or cyanotype over platinum. These were both roughly 300gsm papers.
There was also a slightly heavier paper also called Whatman's Printmaker that was about a 350gsm paper that was only available in the NOT surface. It was acidic right out of the bag, and can give one of the richest and highest Dmax palladium prints I have ever seen - even single coated. The only gotcha was the texture - if you are looking for a smooth printed surface, it was definitely NOT that...
If anyone can track down an old stash of Whatman's Watercolor it is worth trying. My only hesitation in recommending this is that you will have a bitter bout of disappointment after using it and realizing that it is no longer to be had.