>>31 years I worked at Heathrow and TC and never worked on a single Christmas Day. Can't be bad.<<<
Not bad for you I am sure but 31 times someone else had to and you never once paid the guys back. Certainly not something to boast about.
To the original poster, as demonstrated there are a great number of extremely selfish people you will encounter in the job. Things ranging from the traffic dodgers who drift in a couple of minutes after the hour/half hour offering breaks when every body has already rotated to my personal 'favourite' of the guy who refuses to swap a shift then you turn up for that duty and they are in on overtime.
The job is great fun however with plenty of opportunity to do a great deal of different things that you probably would not without various degrees in different fields. You will also be met with much negativity from dinosaurs who are extremely resistent to change because things were always harder/better/faster/stronger back in the day.
Work/life balance is no different to any other shift working job in ATC. There have been many I have known over the years who have a whole other job on the side from Ferry driver to pool builder to cake decorator.
Good luck.