Lancaster Insurance

Well renewed with these a couple of weeks ago. Insured for me main driver and wife named driver. I was asked if I wanted anything else and I said "yes commuting to/from single place of work". I work offshore so it wasn't for me, but I didn't state for me or my wife I expected it would be for both main driver and named driver. When looking through the detail I was covered for this but the wife wasn't, so a phone call to them to let them know I wanted my wife covered for this and they tried to charge me £30 which I declined and told them to go away and listen to the recording which they did.
They now only want £15 as they did not fully explain when I took out policy (there words). I told them I'd pay but that I'd be seeking advice from my credit card company which I plan on doing when I get home next week.
What is it with insurance companies??

I can do better than that, they sent a letter to me a week after taking out my policy saying they was cancelling my insurance as the insurance company would not cover me with my LR parked on the drive .
I called them and was told don’t worry it won’t be cancelled they will find me a different insurance company!
Six months later I received a fine off DVLA for my Lr being on the road with no insurance, Lancaster had cancelled it and not notified me !
Could have cost me my licence, terrible company!