If I see an EML on a surecheck report for an online purchase I won't touch it, however if I'm at the actual sale and it has a light on its not a deal breaker, you can listen to the engine, have a good poke about. I bought a 45k Jazz auto a couple of weeks ago from the auction in person, sounded fine on tickover and with the revs on but EML light on, I buy loads of them and was confident it couldn't be much. Turned out was a crankshaft sensor £33 + fitting, no drama.
I suppose you always trust your own decision over that of some promoted car valeter, sorry..... auction vehicle inspector.