One thing to keep in mind is that the more you order the more economical the ship cost gets. The MINIMUM charge for USPS First Class is $14 I believe. If you were to ship an empty box, that is what it would cost. If you ship one deck to the UK, the shipping costs more than the deck. Not very economical.
If you ordered 24 decks, you could get DHL Express for about $40. Yea, that whole order is expensive, but lets break it down.
Ship cost per deck, one deck = $14.00
Ship cost per deck, twenty four decks = $1.66
While the whole order is more expensive, it is MUCH cheaper (per deck) to ship more decks. That, and USPS First Class takes up to 21 days, while DHL Express takes up to 3 days. You would get a much better value and ship speed with more decks.
If a larger order is not in the cards for you, you could potentially get together with friends for a larger combined order, or you could take a look at magic shops in your area.
// L