I would go back to the vets and look for a change in treatment. Also you probably need to persist with spraying the house until this is fixed, as the cocoons really hang on. From the FAB website:
Quote:
“For some treatments there may be a time lag of weeks to months during which fleas may continue to develop.”
Think you need to move away from fipronil at least for now, and also look at giving your cat Program as it prevents the eggs the fleas which are on him now are laying from developing. From the FAB website, Capstar will affect adult fleas (as should the other effective flea products) but won't do anything for the eggs.
Sorry but it feels to me like you have a big infestation in the house and until that is cleared up your cat will continue to have fleas. And since you say you have 'just moved' it might well be the house was infested when you moved in and you have having to clear up after the previous owners.