I think rumours of the January float started in a comment in The Times but I think that was misreporting so I wouldn't read too much into it. However I think we are looking at the first 6 months of 2000.
I'm vaguely aware of Whatman and it is one I have been meaning to look into. Perhaps Meg or one of the others knows more about it.
As regards when to get into PRM, any sharp rise is ALWAYS followed by a retractment as there are a number of people trying to trade this stock so if it rises (as it did when it was mentioned on SMTM) the MMs allowed it to rise quite quickly but pulled it back as soon as the 50K sales started to appear. Best to look at the chart and don't buy too far off the support line. It used to be quite unnerving buying PRM because the spread used to be about 10% when it was hovering around 45p but the spread is much narrower now so you don't face a loss of 10% the moment you buy.
As has been noted before this stock is not one where you would wish to sell just because you have made 15% but maybe hold for the longer term so long as the market seems to favour biotechs.