Basic Outline of a Business Letter.

Attention grabbing heading (up to 10 words)

(The heading must grab attention - something your prospect will relate to that your proposition will produce - for example, Cost-Effective Sales Enquiry Generation, or Reduce Your Staffing Overheads, or Fast-Track management Training).
When you next consider your arrangements for (product/service) I would welcome the opportunity to understand your requirements and situation.

(Optional) Our customers include (two or three examples, relevant and known to the prospect), who have found (state key benefit, % savings, strategic advantage) from working with us.

I shall get in touch with you at the soonest possible in order to agree a future contact time that suits you/your own review timescale.
 
Yours sincerely