Hi Ian, fancy goldfish are very prone to swim bladder and buoyancy problems,
try adding a small dose of aquarium salt and see if the moor will eat a cooked shelled pea, this will help with the fishs digestion.
Are you currently simply feeding the moor flake food? if you are it would be better to change to a sinking pellet, this will not only reduce the waste produced in the tank but also prevent the moor from gulping down air as it eats the floating flakes. Dry flakes also cause fancy goldfish digestion problems,
Also make sure that the moor is getting regular green foods, this can be anything from aquarium plants to the weekly pea or slice of cucumber. This will all help to keep the fish as healthy as possible.