Used car purchase gone wrong – advice?

Son bought a 2012 Fiesta 1.0 Ecoboost from an independent dealer last Thursday. No issues on the test drive or homeward journey, but that evening the engine stalled, oil pressure light came on, and it wouldn’t turnover for 20 minutes or so. Thereafter it restarted and ran OK again. This has happened twice since and now the engine warning light is orange.

The dealer included a 6 month warranty (provided by Autoguard) which has a £1,000 claim limit per item. Autoguard have approved getting a diagnosis at a local garage but we can’t find one that will take a look before next Wednesday, until which we obviously shouldn’t drive the car. Google tells me it could be something simple like an oil filter or pump, or could be as bad as engine failure. If the latter then no doubt that would be more costly than the claim limit £1,000.

Son likes the car but I wonder if there is a time after purchase during which we can (and should?) ‘reject’ the car and seek a refund. It’s been 5 days so far, and the garage prognosis will be on the 13th day. Not yet contacted the dealer, who is 25 miles away, which itself presents a logistical issue getting it back to them.

Thanks for any advice
Peter