Aw I'm sorry to say it but your a dingbat!

I had a feeling you were going to say that!
Right first things first.. Go to a solicitor and as for the free 30 mins they give out (if they still do that)
Has the relationship between you and your biz partner detiriorated past the point of being able to sit down and sort it out amicably?
Are you being fair in what you want as part of your "out" package (put yourself in the other persons shoes when you think about this too)
A close friend of mine just had to walk away from a £10k investment because they had no contract so prepare yourself mentally for that too, do you have any friends in the law industry you could ask for some help from?