Depending on your insurance requirements check out royal sun alliance. There quote as significantly less than M&S for my home and contents cover including my bikes at home however if I wanted to add cover away from home the policy doubled in price and put it well above M&S prices.
What I found with M&S was that for my renewal this year the cover dropped from 4k/ bike to 2k and that if I was to go online and get a new quote and the 20% discount it worked out more expensive due to new quote having a 1K limit on bikes.
Think I pay about £45 / month for my insurance however I am sure this is being bumped up by some of my neighbours 1 of which who have been turned over 3 times in the last 2 years for bikes in their shed and 2 have lost various bits of gardening kit.