As a landlord i'd have every comeback knowing that I had no control over the security of my property.
doubtful
tenant's are occupying the property and can change the locks regardless
in this instance the locks will have been changed because they were required to do so - I really doubt you could do much about it - requiring the locks to be changed is one thing, forcing them to also pay for some tradesman specified by you is probably not enforceable AFAIK


