ONE year from its consolidation as the single most important terminal operator in Belgium, the Sea-Invest Group is now headquartered in new purpose-built offices at the Port of Gent. Since the expansion that led to the group's singular position in mid-1992, market conditions have severely hit performance at all terminals but the company is confident that its ''full service'' trading position will yield great advantages in the future. Despite concerns, notably from ship's agents and their customers, that traffic diversion and non-competitive rate structures would result from Sea-Invests monopoly of large bulk terminals, the company stresses that competition between Belgian ports is less important than offering a realistic alternative to the Hamburg-Le Havre range. The group says the main advantages of its centralisation have been efficiency and flexibility to customers, as well as a co-ordinated negotiating position with port authorities. Last year, the Sea-Invest Group handled 55 million tonnes of cargo.