By Guy Taylor JD Sports Fashion has completed the acquisition of a 40 per cent stake in a Polish investment group as it continues a push into European markets. Britain’s biggest sportswear retailer said it was now the sole owner of Kraków-based Marketing Investment Group (MIG), which manages a network of stores including Timberland and Umbro. It comes following competition approval from the European Commission in December, which ruled the transaction was compatible with the internal market under the mergers act. JD had originally taken a 60 per cent stake in MIG in April 2021, and since then h…