A tip for St Ives in the summer: Restaurants in town do not take reservations at all, most places are walk-in only, and I've found Tretho Lounge to be amazing!

They have an amazing separate vegan menu (ask for it when they seat you) and have managed to seat my groups within twenty minutes approx which is good going in the summer.

Tretho Lounge is definitely worth a visit, and keep an eye out for their special food and drink offers on different evenings.