Owning your own home

I'd check with the insurer but ISTR my old John Lewis policy used to include all outbuildings too.

I'd assume it only covers outbuildings on the same plot as the house, not a completely separate garage that you rent/own elsewhere.

http://www.johnlewis-insurance.com/homepage/customer-services/policy-wording.html

Theft from outbuildings and garages : Cover 3 and 4 : £3,000

"

1. Theft or attempted theft using force and violence to get into or out of your home.
   
   

(What is not covered)
Any amount exceeding £3,000 for each claim for theft or attempted theft from any detached outbuilding, garage, shed or greenhouse. Loss or damage when the home in which you live has not been lived in by your family for more than 60 consecutive days.
"