you are protected under the sale of goods act 1979, vehicle must be free from fault (asides from declared or known faults) any subsequent mechanical fault discovered within six months of the sale is deemed to have been present and undeclared at the time of sale and therefore is rectifiable at the expense of the seller.
You must adhere to procedure. Give the seller notification and opportunity to rectify faults, if no contact then you can have them rectified and pursue the seller via the small claims court for costs. Cost of doing this will be around 50-100 pounds. In my humble opinion your case is quite strong as the seller published his/her opinion of the vehicle on this forum and is therefore in the public domain rather than being merely a verbal assurance.
Note though a justifiable claim against the seller is only as good as his/her status, should they be bankrupt or"of no fixed abode" this will be a pointless exercise.
really most of the faults are normal wear and tear and can happen at any time
track rod ends the seller doesn't have to know about, tyres inner wall the same, ball joints the same, brake light yes, damage to bumper cosmetic, paint job cosmetic, gearbox not sure, don't think it would fail a MOT for grinding, clutch wear and tear, it has 115k on the clock and was sold with no MOT (i think that bit is a bit unclear to me)
he has in no doubt been bumped for 3.5k but to buy a van with that mileage is just well, very silly
sorry and I feel for the poster, but you live and learn
and there is nothing to stop the seller saying he advised verbally before sale