My wife is from Ireland, so I can vouch for the power of a cup of tea (as well as other liquid refreshments, of course).

Do you think it should maybe be just a little bit faster? As, Vic remarked, it is a comforting song (what could be more comforting than a nice cup of tea?), but the lyrics also have a light-hearted touch to them, describing a happy occasion and urging friends to come over and join in, which might be suited to a more up-tempo treatment. Just a thought.