For some reason since a few weeks ago my EAS has decided to default to motorway height instead of standard.
So when I turn the ignition on and start the engine it moves down from standard to motorway.

It never used to do it, the only thing that is different is that I was using it locked to motorway height a few times shortly before this started.

I've had a standard relay in place of the usual EAS one for a long time now and quite like it, so I left it. I prefer that the car isn't adjusting unnecessarily.

The height lock button is not pressed in or active when this happens.

As far as I'm aware this isn't normal or an option? It should always default to standard height, I think?

That's usually a side affect of taking the timer relay out and putting a standard 4 pin one in. I suspect if you swap them back it'll sort itself out. If you've got no leaks and don't park on very uneven ground, it shouldn't adjust when the timer kicks in anyway.

Ah interesting... I'll have to try that. It's weird that it didn't do that previously when I first swapped the relay.

I rebuilt the valve block and replaced the perished bags last year, so no leaks, I think maybe a sensor is a bit dodgy though, as at random it would go down over night/a couple of days of no use, whilst most of the time it would sit perfectly, sometimes it wouldn't move for a week and still be at the same height. And this is parking in the same place exactly, on a level driveway. Since swapping the relay, it never goes down, so I can only think it is a sensor to blame.
To be honest I kind of forgot about it lately as with swapped relay it's no problem.

I should swap back and see how it goes.

If you are going to be leaving it for a few days, pull the relay and leave it out. If it drops, it's a leak. With the timer relay back in, if it didn't drop with it out it might be a height sensor, but if it was and one corner was being reported as low, it will drop the other 3 to match so you'd find 3 corners had dropped but one hadn't.