I pretty much agree with Antiguru. The Data Protection Act says that information must be held for "specified and lawful purposes, and shall not be further processed in any manner incompatible with that purpose or those purposes". Contacting employees with business-related information is clearly within that scope.
You could, of course, contact the employee and ask him or her for their address, but the point made by Antiguru is a sensible one - why have the employee's address on display? That could cause the employee unwarranted distress.