I like the auto hold function, but it seems to frequently turn itself off between uses - is it meant to be like this? It's fine during a drive, but often has switched itself off after overnight parking.

The battery was new last year and the auto stop start works fine; software is up to date too.

Any other poosible causes?

It's normal, but very annoying. It will turn itself off if the battery SOC gets below 60% but also it turns itself off if you sit in the car with the engine off for more than few minutes. Using the electric parking brake also causes the Auto Hold to turn off, and lastly if there is an 'R' in the month 😂 

I’ve only ever seen it turn off if you don’t have your seat belt on or move the car without the doors completely shut. Something outside its designed parameters and it turns off. I have to stop to open the gate and if I don’t operate the EPB manually it will often disable auto hold. 

Good to know that's it's not just me that has problems with the auto hold.

I still can't believe how they took everything good about the brilliant Mk3, trashed it and turned it into the Mk4.