Mother's Day this year is on 10th March, 2013 in the UK.
Mothering Sunday is a tradition which can be traced back to sixteenth-century England, and although similar in tradition it varies greatly from the American Mother's Day.
In the UK, Mothering Sunday always falls on the fourth Sunday of Lent (directly in the middle of Lent), and secularly it became an occasion for working children to return home in the middle of Lent in honour of their Mothers. For this reason it can also be called Mid-Lent Sunday, Simnel Sunday, Refreshment Sunday, or Pudding Pie Sunday. It was traditional for children to bring home cakes & buns for their mothers.
In the USA however, Mother's Day always falls on the second Sunday in May (meaning that Mother's Day in the USA falls on 12th May in 2013).
Just in case you're wanting to get prepared for next year extra early, Mother's Day/Mothering Sunday in 2014 falls on 30th March!