I always use Centuro, never had a problem, in fact last year someone damaged my hire car while parked at Leroy Merlin, made a real mess with a deep 9 inch gash in the rear door.
When I took it back i pointed it out to the Centuro guy and he said don't worry it was there already! No it wasnt but I wasn't going to argue!
They never did bill me for it so God knows but hey I was well happy.
Like someone said above get annual insurance from the UK its about £40.
Andy