IF you get accepted as an ATCO, you would be entitled to two weeks 'special' leave in addition to your annual leave entitlement.
You are required to declare all 'secondary' employment and NATS have some funny ideas about what you can and can't do, f'rinstance one person who regularly posts on these pages declared some spare time ATC work at a non-NATS unit and part time flying instruction; NATS let him continue with the controlling but told him to stop the flying instruction!
Now I would have thought it would be the other way round, as an incident at his part time unit could result in licence suspension so he couldn't do his main job whilst an incident whilst instructing was unlikely to affect it; you figure it out.