I had the exact same thing about 2 months ago. I had an accident last year, non fault, no claims on injury...then out of the blue some guy calls me up saying the insurance companies have a "pot" of money set aside from the claim and that if I don;t then the company will re-absorb the money and that they would much prefer me to have the money than it go back to the corporation...
I ofcourse was very skeptical about the whole thing and asked them more questions but they couldn't tell me when my accident was or even which vehicle it was is! they said it was a ford escort....not had one for 7 years so that was bogus....his excuse was I may have searched for a quote on a price comparison site for a ford escort and since I would admit there was a claim in the past 3 years they got my information to contact me from there.
I then went on to say i didn't claim for injury because well... I wasn't injured, my back was a bit sore for like 2 days but that's nothing, I could have just slept awkwardly haha! but the guy was very pressuring and persistent.
In the end I said I'd think about it and phone back later (because he had kept me on the phone eating into my lunch hour). later that day I got 2 more calls from the same number which I ignored as I was still working. then the next day I had about 3 calls, then about 1 or 2 every day for the next week. TAKE A HINT!!!
what mad me uncomfortable was it was apparently very easy all I had to do was take 10 mins of my time to give them all the details of the crash and a verbal confirmation I wanted to go ahead...and they the vast majority don't even need you to go into court.
even said to him I'm not happen about it because it because of things like this that is probably putting mine and everyone elses insurances up but he said "noooo this doesn't affect that".....yea... ok..

they finally stopped calling about 3-4 weeks later xD