advice needed: how to sell a customer-base

I am looking for a consultant or marketing executive who can advise me. ======================================================================= My customer stopt his business and has a database with about 12.000 verified (by Experian) records, complete with name, address, city, phonenumber, email, etc. The database has some more information. Who can advise me how to do this in a correct way. The records are from Dutch and Belgium (Flemish) young people who are interested in gifts.