(Reuters) – The cost of a comprehensive car insurance policy in Britain touched an 18-month high in the first quarter and will continue to increase on the back of rising inflation and regulatory changes, a survey showed on Thursday. UK motorists now have to pay about 550 pounds ($718.08) for a comprehensive car insurance premium, according to the latest index from price comparison site Confused.com in association with insurance broker Willis Towers Watson. Car insurance premiums had fallen for a year till the autumn of 2021 as lockdowns kept motorists off the roads and competition in the UK ca…