A micro-site is a method of isolating one of a larger group of products or services into its own free-standing website.
The advantages are:
Customers prefer "specialist" shops or services
Proven increased sales
Better search engine ranking
Easier to get reciprocal links from interest groups
Your "Head Office" website may by now be too large and cumbersome for your potential customers to navigate to find the service they want. Maybe it is time to consider creating satellite sites, each describing one service provision in detail.
Massmedia can advise you if a micro-site solution is appropriate for your business.