If you're taking your Mum for tea on Mother's day, you could also buy her a gift on the tea theme as a memento of the day. The Anzu black tea candle is a bestseller of ours,
vintage teacups are a lovely gift (ebay always has a great choice and they're reasonable too - I like to search for paragon china),
the hummingbird bakery book has a Mother's day section so you could buy it, cook her a cake from it then give it as a present afterwards - a double gift!
The Anzu Bond Street apron in turquoise adds a glamorous touch to baking.
Or alternatively if she is not into baking but has a sweet tooth, you could buy these Vivienne Westwood chocolates from Fortnums. Such pretty packaging.