According to Seth Weinstein, principal of Hannah Real Estate Investors and his partners Paxton and Ray Kinol of Stillwater Investment Management, Fairfield County Bank has signed a lease for a significant portion of the commercial space at Eastside Commons, located at the corner of East Main St. and Lafayette Street.   Eastside Commons, a new luxury residential development located in downtown, will continue the dramatic revitalization sweeping through the area by providing 108 new residential units and 15,000 s/f of retail/commercial space to the cities East Side.   Fairfield County Bank chose Eastside Commons for the company's first branch in the city. It will occupy 4,000 s/f of the ground floor and will offer a drive-through, automatic teller machines and banking services at this location.  The bank will accommodate customers with 12 designated parking spaces and a front entry for pedestrian customers on East Main St. Represented by Penny Wickey, principal of Saugatuck Commercial Real Estate LLC, Fairfield County Bank is expected to take occupancy in the second half of 2008.   Weinstein said, "As the transformation of the east side of the city continues, with more and more housing and businesses taking occupancy, we believe that the bank will fulfill a community need for convenience with both personal and business banking." There is 11,000 s/f of retail space at Eastside Commons remains available for rent.