SSE, the energy company once known as Scottish and Southern Energy, has bought Northern Irish outfit Phoenix Supply, as it continues its expansion on the island of Ireland.The enterprise value of the business is £19.1m, excluding working capital adjustments.SSE, through its subsidiary Airtricity, now provides gas and electricity services to 750,000 customers, or 20% of the all-island total.SSE Shares were down 0.58% by 11:29.BS