You'd think the UK would be alright with it given Irish names are and were reasonably common (at least in parts of the UK), which commonly have fadas in them (i.e. Béibhinn, Seán, Ciarán, etc)
By the way, the accents can often be used to force the right pronunciation of a foreign name on native speakers (at least in US, where Spanish names are so widespread). So e.g. use "á" if you want it to be pronounced [a] etc.