Additional Garage Work
Authorising garage repairs
Garages should work strictly within their authorisation. Some will attempt to contact you should further work be necessary; some do not. You need to make sure that the garage is clear what sort of authorisation you are giving them.
Specific authorisation
If you authorise a garage to carry out only specific work, and to do no other work without further permission, then the garage is not entitled to claim payment for any extra work done.
It may however remove any unauthorised replacement parts fitted provided the old parts are properly re-installed on your vehicle by the garage. If for any reason this is no longer practicable, the garage should bear the loss.
Obviously, unless such limited authority is in writing, it is open to dispute what instructions were actually given.
General authorisation
If your instructions to the garage are simply to carry out necessary repairs without placing any limit on either the extent or the cost of them, you give the garage unrestricted authority to carry out whatever repair work is necessary. This does not mean the garage is entitled to do unnecessary (as opposed to necessary) work, but establishing this is often very difficult, and the task of doing so would be upon you in the event of legal proceedings.
If you are in doubt set a financial limit, preferably in writing, and ask the garage to contact you beforehand for your authority if this is going to be exceeded.