[Kav]

This is WINTER. You never, ever wear summer whites in winter in nautical kit.

I met a Weimar Kreigsmariner who fled nazi Germany whose work with the british is still classified.
Fascinating old gent, he came to a military wedding in full uniform boasting both the Iron Cross 1st class and all these R.N. medals. That got looks!

It's best to ask your host.

 

[Kav]

Alternatives could be the Johnny Depp/John Belushi Pirate look or, my favourite; crumpled cap, white turtleneck under grey leather coat with a pair of 9x50 bridge binnoculars with untrimmed beard.

Now I know why I stopped wearing my old issue peacoat.