Telemarketing/research/database compilation - City of London companies, staff benefit schemes

I need a database of large companies based in the city of London, who would be interested in staff offers that they would communicate via their intranet/staff newsletter or other staff benefits schemes.

I need contact details for interested HR Manager or Benefits Manager or similar person. I will need Name/email/phone number.

The scheme is for companies with over 500 employees that have an interest in staff offers/benefits and they do need to have a good system for communicating them.

I am not interested in any company that wants to charge a fee for promoting special offers to their staff.

Please quote on a per validated name/company basis.

I need a maximum of 20 contacts to start with as a test but if this is successful will definitely want more.