Yes Huw your observations on MQA quality are based on NOT hearing MQA!
Bit perfect replay is essential and also blue or green light on the Explorer. So no upsampling, volume control at 100% and 24 bit resolution.
There are many files available on 2l website to do a proper comparison. See separate thread in decoded MQA.
If no coloured light with VLC (and there are some posts on web re bit perfect replay with VLC, then suggest trying, for example, AUDIRVANA as recommended by Meridian. You can trial it free!
Good luck....