Naples is about 2 hours from Miami or 4 hours from Orlando. You could fly via Heathrow to Miami or via Gatwick to Tampa (again about 2 hours, but BA don't go to Tampa every day, whereas they (and plenty of others) go twice a day to Miami. Therefore you can usually get a good price on a Miami flight. You could have a look at e.bookers.com or flynow.com both of whom usually have good prices. Don't know how far www.opodo.com go in advance, but their prices are usually quite good. however, as Alison says, a travel agent may be your best bet.