Just like the heading says, I received them today! Popped them in my Motorola L6 and my daughter's Siemens M55 (both are unlocked) and the sim cards are ACTIVE!
I actually even received a text message from a promotional long distance company in the UK, more proof that the sim card is active. All I need to do now is top-up the cards when we arrive at Heathrow!
THANKS to all who replied

. Now I am able to give my UK cell phone # out to the shuttles I've arranged along our trip, as well as our relatives who we will be meeting up with.