i'm assembling this:
It lacks the basic parts that you need for Royal Navy version. AFAIK in Poland there is no available HR.3/4. In general, apart from a few slight errors and imperfections the model is really good.
More about the colours - I thought that the Dark Green/ Dark Sea Grey was used since mid 1950 and the date of this particular picture is February 1950. I'm not sure if it changes anything though.
I think that the cockpit colour is Interior Green lighten up by sun light. Or maybe there is some other color that might have been used by RAF that you know of?