Rumours were that Apple Pay was coming to us round about the same time as the Apple Watch but I gather that not enough contracts are in place with the various financial institutions yet for this to be a reality. Currently the word on the street is the second quarter of 2015.
Unfortunately there is no way to attach a card to your Apple Pay account in the UK yet. When I moved out from the UK to the US, the option pretty much magically appeared on my device. My girlfriend back in the UK doesn't have this option at all, as we compared devices.