Hi Mickky The original was covered in Cortisone similar to the old linoleum floor covering. Most models have painted decks. I suggest you browse through the build blogs and Forums to see how others have finished their Fireboats Dave
the rear well deck was planked, the area where the tow hook is was planked, (see original plan pic, in front of the tow hook you can see the planks) the outer decks where painted in cerrux none slip paint (see original Vosper plans with paint codes etc)
Info taken from original plans, I replicated it on my four footer like in pics. My build blog is on here somewhere!
I did the none slip finish using stone effect rattle can paint from B & Q, several light coats until I got the texture I wanted, then painted over that using the BS paint code as in the plans.