I have been riding there in either just shorts (and loads of sun block), or summershorty, and a few times in my short arm long leg 3/2 summersuit (when really cold, or just before sunset when going far out).
Live in Denmark so used to this water, just like you - and the wind is much warmer so you dont need much suit, more of a sunblock and in case you gotta be in the water for a long time.
Watertemperature is quite pleasant down there IMO, eventhough not warm so a bit of suit is usually required..
Some are just in a shorty, works fine, others have been using their old 5/3 wintersuits, so everything is possible - but long arms/legs so you keep the sun away, and can swim for long if necessary, and a really thin suit say 3/2 as no reason to choose a less flexible one, is IMO the best overall for most riders in that area
I think your 4/3 cut legs are perfect, eventhough you might be REALLY warm when on the beach, but hey, then you got a reason to hurry out and ride all day instead