Thanks all. Not the answers I was hoping for, but I see now I'll be stuck on the country.

Cancelling and rebooking isn't an option because this was a sale fare booked to take advantage of significantly cheaper business class ex-DUB, so a fresh ex-LHR would be prohibitively expensive. I know it's cheeky to ask them to change that to an LHR departure but figured it would be worth asking.