CONSTRUCTION of the final stage of the Custom House Plaza development at Dublin's International Financial Services Centre is to begin shortly following the clearing of the site. Dutch bank ABN Amro and Riada Stockbrokers are to occupy 42,000 square feet in the first stage of the scheme, which will be completed next May. Lisney in currently involved in negotiations to let about 50 per cent of the remaining 75,000 square feet in the first phase. The agents are quoting rents of £27.50 per square foot.