How to go about written a letter to get a sponser for a music event

Hi everyone

I am setting up a Clubnight called isolation which is set to start touring uk clubs and venues this coming summer 2011, Isolation is all about giving djs in the area of the gig their chance to shine aswel as a main name to headline the act our 1st night is in edinburgh april 2011 i am wondering how i should go about sending an email to a company asking for sponsership and what i should say we are offering them main advertisment space on the night and there logo on all advertisment materials but me and written dont go to well together as i have dislexia so i have no idea in what to say any help would be much apreciated

Thanks

Iain M