LONDON―Growth in euro zone business activity slowed this month as firms faced soaring costs due to supply-chain constraints, while the bloc’s dominant service industry struggled amid ongoing COVID-19 concerns, a survey showed on Friday. IHS Markit’s Flash Composite Purchasing Managers’ Index (PMI), a good gauge of overall economic health, fell to a six-month low of 54.3 in October from 56.2 in September. That matched the lowest forecast in a Reuters poll which had predicted a more modest drop to 55.2 but was still comfortably above the 50-mark which separates growth from contraction. “The October PMIs are consistent with our view that economic growth in the euro zone will slow markedly in the fourth quarter, and that inflation will rise further in the coming months,” said Jack Allen-Reynolds at Capital Economics. Supply chain bottlenecks caused by the coronavirus pandemic, alongside a shortage of heavy goods vehicle drivers, meant the input prices …