6 days into ownership and still finding my way around the car - 70th Anniversary 4/4

The car had/has a satnav mounted under the dash which doesn’t seem to work. It powers up but the gps isn’t updating my location

Anyway, I want to replace it and there’s a panel under the dash the the current fitting it attached to - is the panel normal fit?

Also, what is the small button for - any ideas?

[Linked Image]
[Linked Image]

4/4 70th Anniversary