LONDON (Reuters) – Activity among British construction companies improved unexpectedly last month, although the outlook darkened as growth in new orders dried up, a survey showed on Thursday. The S&P Global/CIPS construction Purchasing Managers’ Index (PMI) rose to 52.3 in September from 49.2 in August and was above the 50 threshold for growth for the first time since June. Economists polled by Reuters had forecast a fall to 48.0. “UK construction companies experienced a modest increase in business activity during September, but the return to growth was fuelled by delayed projects and easing s…