Billy, I'd play this dealer as hard as you can; they are on the defensive after ****ing up.
http://www.volkswagen.co.uk/used/what-approval-means/tab8And I quote
Our skilled, Volkswagen trained technicians carry out a comprehensive workshop inspection of every used car before it can become an Approved Used CarThat's what I'd be using to batter the dealer principal with, and use it to make his service manager beg for his/her job. Complaining to VWUK that the dealer didn't meet the required standards of used car checking would be very high on the list too.
Once you have the dealer on the back foot and apologising/offering sweeteners, I'd demand from them,
in writing that they will warrant any bottom end engine faults, particularly any that are possibly attributable to oil starvation.
God only knows how many halfwit car owners drive around with oil lights on. Modern cars don't implode simply because the oil level is low. If they did, the hard shoulder of the motorway network would be littered with drooling idiots gazing at conrods and cranks strewn across the carriageway. The orange 'warning' light is just that; a warning that you need to top up your oil. A fuel warning light gives notice that you need more fuel in the same way. It doesn't come on when the engine is about to sup the last drop in the tank.
So nail the dealer for service worse than most backstreet garages; bear in mind that you pay a premium for a dealer-network "approved car". And you just paid that premium for sod all. I'd want some sort of sweetener for that as well as a guarantee against engine issues, and the Service Manager's head on a plate.
But I wouldn't hand the car back, unless you get to day 29 of your 30 day period and havent had satisfaction from the dealer. Then I'd ring the principal & tell him to collect it and ram the car up his hoop. Sideways