Don't feel like it's all too hard because of the bipolar. The only thing on that I wanted to mention is that if you're on medication and taking it as prescribed and you're still feeling the symptoms, you might not be on the best medication for you, or you might be on a great med, but not quite the right dose. Either way, I'd visit the GP that prescribed them and let him know that it's still a problem. Hopefully if you can take the bipolar out of the equation, the eating issue will get a lot easier to manage.
Re gastric banding, my mother has a friend whose daughter had a binge eating disorder and had the surgery. Unfortunately it didn't help her. For some it works, for some it doesn't. There are risks and side effects involved so make sure you ask about them at your appointment so you're well informed.
Stress plays a huge part in disordered eating, whether you eat too much or too little. Quite often it's a way that we can feel in control of a basically out of control life, or receive comfort from satiated taste buds when no other comfort is available. I'd advise having a look at mindfulness on wikipedia. There are a lot of easy to read books on the subject such as '8 Keys to Mindfulness' that I would recommend. Things get a lot easier when we're not so stressed. Different systems kick in to our body that reduce the ability for rational, logical thought and the reactive parts of the brain kick in instead. That's not great for sticking to ones well thought out resolutions. But it's also very normal and it's a struggle for everyone to override impulsivity and retain executive control over your brain!
Other than that, I still recommend thinking of something that you love doing and that makes you happy. It might be as simple as reading a book, getting a new pet etc. but it gives you something you can throw yourself into when you start to feel bad, and you won't have as much time to eat.
If you decide to diet again, I'd be really careful about losing 5-10kg in a week. Stopping eating 'cold turkey' isn't a good solution and can really damage your health, as well as causing huge increases in anxiety (bye bye executive thought processes). It's better to measure out a small portion of food, put the rest away and then STOP when you finish it. You can enlist friends or family to help you stick to your resolve!
Good luck with your appointment, your decision and the bipolar meds.