I've had a couple more of these calls last week. I tried to ask a few more questions this time and the company calling me were calling on behalf of a bike insurance firm that I do not have insurance with.
I think what is happening is that when you fill in a car/bike insurance quote form online all this information gets sold, and if you've said that you've had a claim, these companies then sell your details to 3rd party ambulance chasers.
So - moral of the story is only go to reputable insurance brokers online and read the T&Cs before filling all those boxes in!