Hi Greg,
As Ron rightly surmised your model appears to be of the launch Sir Humphrey Gale.
Perkins themselves describe it as 'semi-scale'.
To me it's a highly simplified semi-semi scale version🤔 The front and the rear of the cabin structure are considerably altered☹️
Compare the Perkins pic (#1) with the three pics (2, 3 & 4) of the real boat operating in Portsmouth around 2011/12. Note Ark Royal in the background of pic 2.
Pic 3 shows an armed officer on the stern which gives an idea of size.
Pic 5, also in Portsmouth shows a pair of Type 45 destroyers in the background😉
I also found on vesselfinder her sister ship Sir Evan Gibb operating in Gibraltar Bay.
See link below.
Vessel finder gives her dimensions as LoA 18m, Beam 4m.
Thus a model length of 0.41m gives a scale of as near as damn it 1/45.
So given a 6ft (72inch) crew member scale figures would be 1.6" or ~40mm.
The pics also show the deck fittings, e.g. cleats/bollards quite well so you should be able to estimate the sizes and make good approximations for your model, or find near commercial equivalents.
Bon chance mon ami🤞
Cheers, Doug 😎
https://www.vesselfinder.com/vessels/details/235026716