cammd said..
I work at ideal/rexel electrical, I stock and sell marine twin in three sizes for the 12/24v circuits, for 240v circuits I sell H07 rubber flex in different sizes and for battery and windlass I sell the welding flex which is a flexible sdi we keep up to 95mm, it's not tinned like the other two.
Most would go smaller sizes where they can because of weight, space and cost, wiring the whole boat in 16mm will cost a lot more than using the smaller sizes where you can
This would be my recommendation. Rexel, MMEM or one of the other electrical wholesalers would be my go-to. If you're going to be spending more than a few hundred dollars, if you can it's worth settting up an account (even a no credit account) for the pricing. It's often a big difference between cash sale prices and trade account pricing.
Or you could sweettalk Cammd :)