Any way to access Control Centre in landscape on the X?

yes, just swipe down from the top right corner (at least it works for me like that in landscape mode in safari).

 

Swipe down from the top right.

 

Swipe from the left and you get a horizontal lock screen for notifications.

 

If the phone is locked, pull from the corner that would be top right if you were looking at the time display correctly. I'm assuming that's what you mean about a clock.