[Cuthbert]

I'd accecpt nothing less than the condition it was in when you gave it to them. Stand your ground & make them rectify the situation.
Not sure if you're in a trade union or not, but mine has a free legal help line with advice on absolutely anything. 1st stop before taking any legal action (if it comes to that).
If you don't have access to such advise, PM me with all details & I'll find out what I can for you on where you stand & what you can do about it.