Hello Jeff,
Whenever you take out an insurance policy with a UK firm, they have to advise of the companies official complaints procedure.
Check your policy documentation for details. There is no coverall guidance I can give regarding individual companies procedures, but if they have run their course then you can usually lodge a complaint with the Insurance ombudsman, again details of how to do that must be provided by the insurance company or brokerage.
A simple but important note:-
Be honest, dishonesty is fraud, and more an more insurance companies are pursuing fraudulent claims vigorously.