If you want an honest reply to your question, I think this is a classic 'not wanting to accept something as your problem' scenario - if you want to diet, do it. Your partner shouldn't have to diet as well. It might be quite insensitive for him to eat take aways infront of you, but I think it's very unfair for you to expect him to change his habits and lifestyle just because you want to change yours. Isn't this just a classic case of misery loves company? It's your diet, not his. :)
Again, isn't he your boyfriend, not your fitness instructor? Exactly how is he supposed to help you to exercise? Sorry, dizy, but you need to take responsibility for all this, not blame your boyfriend. If he had suggested you go away on a curry tasting weekend, wouldn't you be horrified? That's probably why he doesnt' want to go to bammington (I don't know what that is, but presume it's some kind of fitness experience!?)
Good luck with it all BTW.