Brake noise is quite common on the MK1 Scenic's. I'm not even sure it can be fixed.
As for the dent, we'll I guess they'll say it's up to you to look for these things rather than them point them out. Not really honest trading, but then used car dealers aren't well known for honesty
I would have thought you have a case on the belt tho, if it was at 59K when you bought it. I believe the window is 55K-72K or 5 years