It is highly discouraged to go to a company directly and purchase a cover as in more ways than one you will be short-changed when the time comes to pay the claim. You will find that the requirements for you to get paid a claim can only be handled by an agent or broker as they will go the extra mile to make sure that you are properly sorted out.
These insurance intermediaries will also advise you on the best insurance company to insure with as they have the knowledge which most likely you do not have. I always point out about those insurance clients whom we once saw knocking on the door of an insurance company whose doors had been closed for good, but were pleading to be let in and purchase a motor insurance cover.
That is the tragedy of not trusting your agent or broker as you might find yourself holding onto a useless piece of paper known as a motor insurance sticker.