You could have a look at the demographics of the area you intend supplying. Most of your target customers will more than likely be within band A, B or C1 (these are based on proffesional, Management, Middle Management & Supervisory ect).
Your local business link office/contact may be able to help with postcodes for the above in your target area. You could also consider using a speacialist company who could do it for you although they can be very expensive for a start up.
Good luck