Well, at least it's the same language as "Sean". which means that English speakers will mangle it as much as they mangle Sean, perhaps more because it's a bit mroe common in the |english speaking world. But people with Gaelic names who insist on using Gaelic (Scottish or Irish) spellings for them should perhaps not be surprised when the Gaill Wogs Sasunnaich Anglophones mis-pronounce them: the rather well known singer Eithne ended up using the spelling "Enya", most people whose name is Seumas use the Anglicised spelling "Hamish" (sounds like the vocative form, Sheumais), every Ailean I know spells his name "Alan" when communicating with Anglophones, "Cailean" spells his name "Colin".

Of course people keep on telling me there's a misprint on my passport or on my driving licence, and so on; the UK passport and identity service doesn't tell me that, those people have either more sense or more knowledge. I use either the name Tom or just the initials C M when in English (or indeed any non-Gaelic language) and don't get any mispronounciations (although some do insist on expanding Tom to Thomas, which is no name or nickname of mine and never has been).