WARSAW (Reuters) – Ukrainians in Poland will be able to convert hryvnia bank notes into Polish zlotys from the middle of next week as part of a programme involving the central bank, the National Bank of Poland said on Thursday, in a boost for refugees who have faced difficulties exchanging money. Many exchange offices and banks have thus far been reluctant to accept hryvnia given the oversupply of the currency resulting from the large numbers of refugees entering Poland and concerns about its decrease in value. The National Bank of Poland (NBP) said it was cooperating with the country’s larges…