So, an update. On Tuesday afternoon I was going to change the air quality sensor so, as I always do when changing something, I disconnected the battery. Unfortunately, I ran out of time, so I left the battery disconnected overnight. I replaced the sensor and reconnected the battery in the morning and cleared the normal illuminations on the dash. After about 15 mins of driving, I heard the confirmation “bong” for something and my seat then moved to my saved driving position. No idea if the battery disconnection reset the seat module, especially as it’s probably not a permanent live unit. Still, it’s up-and-running again so that’s a ridiculous sum saved for a new or used module and a contortionist job avoided to replace it!