I found M+S on a price comparison website several years ago and am still with them. This years fully comp premium with 2 drivers and European breakdown cover (difficult to get on 18 year old car now) is £265. There is some weird rule in the insurance world that if you already insured with a company they cannot alter some of the terms on renewal, that's why I have to stay with them for the European Breakdown. 5000 mileage limit.
They make their money on unwary customers on renewal. My renewal came in at £330 but on telephoning them to get a better quote they "found" one, the £265, but with the same underwriter and identical cover so I guess they took less commission.
Let us know how you get on.
See you Andy
Frank