the sale of goods act is a bit of a grey area really in regards to second hand/used items.
if the paperwork states sold as seen and no warranty then you will probably get nowhere.
on a test drive you should have been aware of a wheel bearing problem.
our 206 showed up a wheel bearing problem on the test drive and they sorted that before we bought it.
the best thing to do is get on good terms with the dealership, i believe there is a cooling off period for any items bought as long as they are returned in the same condition they were bought. proving the damage hasn't been done since could be a problem though.
just my 2p's worth.