I recently celebrated a big birthday. I live in The Netherlands and the party wad in England. Most of my presents were gift cards for U.K. shops that do not have any branches over here. I will probably not be able use the gift cards until my next visit to the U.K. in August. Should I send Thank You cards for the presents now or wait until I have bought something with the cards in August where I can write in the card what I have bought with their present?