If you are getting bothered by these people, when they call, ask to be added to their "Do Not Call" list, any company that calls people selling something MUST now by law have a "Do Not Call" list, their systems must check against this list and will not call any numbers that are listed in it. tell them that you will give them 24 hours for this to take effect and after that, if you receive a call from them you will consider it harassment and contact ofcom. MoreThan insurance contacted me within an hour of my doing a quote on their site - as it transpires their quote was £50 higher than my existing renewal.
Good luck!