Personally, I would get an RAC inspection done as unfortunately, the dealerships don't really do any testing of the cars they are selling, apart from short test drives by potential customers. Make sure you negotiate hard as gas guzzlers are not moving. Merc warranty is now full for cars with over 50K miles and under 100K. Get the MOT done within 6 months of purchase, at a Merc dealer, as they will find anything that needs doing and you can get it done under warranty. Mine has done 67K miles and needed a few things doing that the Merc dealership had not spotted (same as my last used Merc, different Merc dealership). Hope this is useful.