manticlimactic pretty much nails the reason why your renewal is high.
I used to work for probably the best known UK company (which has been mentioned upthread ;) ).
You CAN take it off auto renewal, insist and it will be done. They'll try tell you it'll cost more but it's bullshit - if the price is too high then call again.
Even if it auto renews at a ridiculous high price - call as soon as possible and complain, it can be reduced to something your happy with and you'll be refunded the difference.
Pay attention to dates on letters sent to you - it has been known that the auto renew letters that should be sent out around 6 weeks before (to give you the customer a chance to call if you're unhappy with it) to actually reach customers AFTER the auto renew has happened.
It's always cheaper for new customers - it's simply to get new business.
If you use the service the maximum no of times that your policy allows then you can expect the quote to go up next year as there is whats known as a service premium. If I remember correctly an increase of roughly £60 was typical and not what they try to quote.
Also while I'm here - Eg,
you bought cover for your car 6 mths ago but you've now got rid of that car and bought a new one from the garage that comes with free breakdown repair for 1 year.
-You don't need 2 sets of cover but the one you bought for the old car can't be refunded - many people either A) just leave it or B) call to try and cancel it - you CAN simply freeze it.
Call up, explain and give the date your free cover runs out and the account will be set to kick back in then - you don't need to lose out, it's your money that bought it and not many customers are aware.