By Charlie Conchie A tie-up between Nationwide and Virgin Money has got the greenlight from the competition watchdog today, paving the way for the £2.9bn deal to close in the final quarter of this year. The Competition and Markets Authority (CMA), which opened a probe into the deal last month, said in a statement today the combination of the two firms was a “relevant merger situation” that would “not give rise to a realistic prospect of a substantial lessening of competition”. The decision will now clear the way for one of the biggest shake-ups in the UK retail banking market in years, with th…