Hi and welcome aboard. You're doing the right thing by thinking carefully about introducing a kitten to your household. A two-bedroomed flat should be adequate space, provided you're prepared for the cat to take control of most of it
He/she should also be fine as an indoor cat - as you've already realised, keeping them stimulated is the main challenge and that can be difficult if you're out most of the time but lots of us work full time and have Bengals that are perfectly happy. It sounds as if you'll have plenty of time to bond with the kitten before you have to be out working.
I would strongly recommend another cat - it doesn't have to be a Bengal, lots of us have Bengals and moggies who get along together fine. Personally I would say get the two of them at the same time if you possibly can, or don't wait too long as the older and more territorial the first one gets, the harder it will be to introduce another one. That doesn't mean it can't be done but the process is likely to be easier and less stressful for you all if they're introduced together or while still quite young.
Whereabout in Manchester are you going to be? I'm originally from Chorlton, although I've lived in Cumbria for the past 20 years.