I am sailing tomorrow (Yey!), but I'll need to buy food as soon as I arrive for Guinness' babysitter. Guinness will be switching to James Wellbeloved lamb while on the ship, so I'd like to keep him on that.

The sitter (Ellie) suggested sainsbury's supermarket for food. But I suspect they won't carry quality brands. Maybe I'm wrong? What stores will carry the JW food?