Work/ life balance is generally pretty good. Whichever unit you work at (I'm talking NATS here but I'm sure it's the same elsewhere), you will get a decent amount of time off from work. At some of the smaller units, the shift pattern might be a little more restrictive but we generally get a good amount of annual leave to use too. I've worked at a smaller unit and now at a larger one and there are pros and cons either way.
Doubt very much you'd be committing yourself to a lonely life of bachelorhood if you hadn't found anyone beforehand! As said, there is plenty of time off to do whatever it is that you do and if you work at the larger units, than there are plenty of people to socialise with. The smaller units, from my own experience, can give you a decent social life too. It all depends what you make of it all really.
Whilst I have a bit of an interest in aviation, it's not the be all and end all. It'll make the job just that bit more interesting if you are interested in it, but rest assured there are many people that I work with at either end of the scale. Those that are on the lookout for certain aircraft registrations and those that couldn't care less about aircraft, as long as they take them on their holidays.
Good luck.