Home contents insurance advice

Time for renewal; our bikes have changed their value. Still M&S or someone else? They are a little pricey this year ...

A friend of mine just got fucked over by insurance (Aviva) who said they cover bikes outside residence but when it came to replacing the stolen bike they backed off; lots of grey areas* BUT they could've paid if they wanted to

• bike was in a locked garage which is used by work to store stuff and there was a delivery happening at the time and it was open so the thief walked in with his shitty bike and walked out with my mates shiny tokyo fixed bike. The bike was unlocked and so were the other 10 in the garage on vertical stand. Insurance said the bike wasnt locked (that is not required if its in a locked premises) but then the garage door was open. The guy in charge of deliveries washed his hands off any responsibility. No bike; no insurance money.
  
  

Thankfully I didnt ride that day having ridden 70+ miles day before otherwise it'd have been my bike. I feel really bad about that. Now everyone locks their bikes in the garage and mine (being the most expensive) is inside the office in cleaning closet.

tl:dr Should I stay with M&S at £80 per month or switch?