Only replace the pipes that are seriously corroded.
Never heard of having to replace the complete set.
Is this an MOT failure or just an advisory ?
As what Keyser has said.
I have all the pipes in stock, however I doubt very much that you will require them all.
Are you running Brembo or JDM calipers ?
I would get the garage to more specific on what is required.
Could well be just surface rust which will clean off and then you can give them a good coating of grease to prevent further corrosion.