Insurance - losing no claims bonus between insurers?

[Chicane-UK]

This has only become a problem in recent years it seems as I've accumulated no claims bonus. I will try and explain the problem and see if it makes sense, and see what people can suggest!

2 years ago, with a then total of 9 years No Claims Bonus I took out an insurance policy with Chris Knott insurance. They said that 9 years NCB was the maximum they accepted, so I asked when taking out the policy whether they would provide me with a letter should I choose to change insurers saying that despite them not recognising more than 9 years, I had earned an additional 1 or 2 years with them. They said "Sure!". Lo and behold, this year they seemed uninterested in offering me a competitive quote so I took my business elsewhere. When I asked about the aforementioned letter I was told this was "something they didn't do" so I'd essentially lost the last two years of no claims bonus.

I subsequently took out a policy with Aviva who seemed very well priced. I've subsequently discovered they only recognise a maximum of 5 years no claims bonus! Am now worried that when it comes to renewal time next year, I will basically have absolutely no proof of the additional 5 years (or 7 if you ignore the shafting I got from Chris Knott) no claims bonus when I take my business to another insurer.

Has anyone else run into this problem before? What did you do? Why is insurance such a ridiculous, convoluted, awkward system in this country!!

Thanks in advance.