Wow! What a menu @Dailyhandtowelwash! How I envy you being able to go out.
From a quick look, it strikes me that you could have most things - it's more a case of singling out the very few that are carby.
In which case, when it comes to the starters, I'd avoid:
Potted smoked haddock and mussels - the sauce may be thickened with flour
Tempura prawns (batter)
Garlic king prawns - unless you have the willpower to leave the garlic bread!
The warm scallop salad, because it has balsamic in it
The coquilles St Jacques, because of the mash
The chargrilled chicken Caesar, because of the croutons
Parma ham, because of the fruit
Avocado salad, because of the fruit
Wild mushrooms, because of the toast
When it comes to the mains:
Many of them are served with Jersey new potatoes - ideally avoid those, but new potatoes are the 'least worst' option when it comes to potatoes, and as you're unlikely to have a huge plate of them, this wouldn't be too bad (and they're so delicious!)
Otherwise, I'd avoid"
Beer battered cod - batter/chips
Oven-baked cod fillet, because of the foccacia and chickpeas
Quayside luxury fish pie - sauce may be thickened with flour, and it will be topped with mash
Both surf & turf, as they come with fries (unless you ask for something else instead)
Obviously the pasta/risotto dishes!
Panfried breast of chicken/soy glazed duck, because of the dauphinoise potatoes
Quayside burger - unless you're happy to have it without the bun or chips
That looks like a long list, but actually there's a whole lot more that you can have - what a difference that makes!
Hope you enjoy it.