Ive done 2 weeks at deutsche bank and going back for another in the summer, as they asked me back again. Firstly I must say that the most important thing to get into IB is most definitely the contacts you have and work experience!
Of course they want someone with mathematical knowledge, but this is not completely necessary as they teach you loads of stuff during your first year in IB, like sending you on courses etc.
Another thing is do not think that IB have set hours, they most certainly dont! The last time I was their, there were a couple of people that hadnt been home so they had worked from 8am on the tuesday and went home at 11am the wednesday, and might i add this wasnt just a one off.
IB is very varied in the amount of roles you can do, but you really need to look into the possibilities, to make sure you choose the right roll for you.
The people I met, knew exactly what their role was, and also what everyone elses in their departments involved. They were all pleasant people considering the crazy hours they have to work.
Personally, I think, the most important things you need to be are motivated, good communications, and have good time management including meeting deadlines.
You also have to be able to get along with everyone you work with, not only because you are in the office for long hours but also because you dont know who has an influence on getting you fired etc, people throughout the entire bank talk, and if they feel you arent up to it you'll be gone
Oh and I also spoke about Unis the last time I was there, obvs if you go to a top one it adds to your CV, they do look down on low/'rubbish' unis, but if you go to an average one they dont really take it into consideration, like i plan to go portsmouth and they said that'll be good - im doing european business w/german
So to be honest I would stick to the business degree if its what you want to do, for one you will more likely get higher like a first as you enjoy it and also, you are paying a high price, and going to have to spend the next four years doing it!