Earlier today, Nik posted about the new BBC shows on iTunes. For the equivalent of about $3.75 each, you can download and purchase your UK fix -- Gene Hunt, Captain Jack, whatever -- assuming you have a way to create and fund a UK iTunes account. For now, the best way seems to be eBay. A quick search of iTunes UK produced a half-dozen auctions, most run by the same vendor.
A £15 iTunes card (good for about 7 episodes) seems to be running in the low $20's but one went recently for $61--I'm guessing the buyer thought he was buying in dollars not pounds because $31 is not an unreasonable price, while £31 is. If buying, make sure you figure out in advance whether you'll be shipped the card (which can run as high as £5!!) or sent the code by email (should be free).
If you already have an unfunded iTunes UK account (google for it), you might be able to find a friend to send you an email-based gift certificate. These start at £5 and go up to £75. If you can work out a deal via PayPal, you could pay your friend, for example, 110% of the face price to cover time and expenses.
I actually did try buying a card directly from the UK Apple online store (free shipping!) but it balked at my US address. Do you have a better way to fund a foreign account? Let us know in the comments.