I live in London and would like to sell a 200 kr. Faroe Islands banknote. This should be worth about £20 by the way.

I learn the currency is equivalent to Danish crowns, but none of the UK banks will buy it (hence, I am told by a money changer, that they will not buy it because they cannot sell it onward to a UK bank).

There ought to be an easy solution here that doesn't involve me flying to Copenhagen...