With Limited currency pairs and iOS application-only transfers from British isles and Europe, Atlantic Money could be the cheapest solution, that has a flat £3/€3 cost (for almost any amount of money as much as a £1 million). None of the other options I tested could beat the overall amount https://vuf.minagricultura.gov.co/Lists/Informacin%20Servicios%20Web/DispForm.aspx?ID=11361595