My previous s-tronic/DSG cars have had a hill-hold button but not on the VRS, was it an optional extra on the Octavia?

All DSG normally have the hill-hold feature IIRC, but as the Octi only has manual parking brake there is no switch for it. Your previous car had electric parking brake didn't it ?

Yes it did. So in the Octavia I guess it's always on then

If you mean 'Hill hold assist' which holds for a few seconds when you have the brake pedal pushed and move to the throttle then that is always available.

 

With Auto Hold when fitted you can choose to have active or not as you had previously.