Unfortunately we do not have the paperwork, but speaking to someone I know in insurance, they said that unfortunately your suit is classed as a "second hand" suit, and that is all that the cleaners are liable to pay you for regardless of how many times it has been worn .
Your arguement could be that your suit is not an everyday suit, so does not have every day wear and tear , also that this is human error, by thier staff, not a "risk" which you take when a suit is dry cleaned where cleaning solutions do not suit the material , and as it is human error, then you should be given full costs of a like for like suit , you should not be out of pocket for thier mistake.
Also, you need to find out what is the contract when you take your suit to be cleaned, unfortunately all you get is a slip of paper, so they know what suit it is you are collecting on your return , I know I have never read the small print when Ive taken something in to be dry cleaned .
Failing that, as mentioned previously , get in touch with the Association of Dry Cleaners, alot of companys think that if they dig thier heels in and say no, then eventually you will go away, DONT give up, keep on persuing it . We had an absolute nightmare with Morrisons at Bredbury over my husbands coat, they initially offered £20 , eventually we got the full cost of a new coat but it wasnt without standing a firm ground .