Research for creation of B2B database

Small company starting direct mail database for inhouse use.

Have list of company names, need to find postal addresses. All in United Kingdom, all publicly available from online sources ( Yellow Pages , Google etc)

Will provide contractor with list of 1,000 company names initially in MS Excel format.

Have c15,000 company names would like to populate database with, ongoing work if initial 1,000 done to correct standard.

Need to get this finished reasonably quickly, so please indicate availablility/ speed of delivery / any relevant experience when bidding.

Thanks