Sorry I cannot help on the legality side of things but that's just plain shoddy IMO.
I had a similar experience when I booked my bike in for a full service (inc. a full brake caliper[s] refurb). I picked the bike up and it was only a few days later that I saw my mate behind me (who had his son on pillion) was waving madly in my mirrors.
My rear brake caliper was dangling from the brake hose and was 'dinking' off my wheel spokes as I rode along - I'm so thankful I was on a motorway and didn't make any left hand turns..........
When I got home I made sure everyone I know who's into bikes knew and I vowed never to darken his workshop again.
PS - it wasn't like it was an inexpensive invoice - the guy knew how to charge!
Hope you got some sort of satisfactory outcome mate.