ONE of the leading computer engineering design companies, Silicon and Software Systems, is to assign the lease of its headquarters building in Sandyford Industrial Park in south Dublin. The company is moving to new premises at South County Business Park. Sherry FitzGerald is seeking a tenant for the 18,500-square-foot premises, Ballymoss House, which is rented at £130,000 per annum - the equivalent of £7 per square foot. The premises, which date from the mid 1980s and early 1990s, occupy a high-profile corner site in Sandyford. There are two interconnecting buildings with both cellular and open-plan offices set around a courtyard.