Hi pickles, apparently SU! should be launching in the UK later this year. So hopefully we haven't got too much longer to wait! I'm very lucky, my friend in the USA sent me the last SU! catty - and she's promised to send me the new one also.
I'm sure as soon as anyone knows a launch date for the UK it will be posted for us here on SCS!
In the meantime, try the Buy/Sell/Trade forum
here to see if there are sets that you want and someone may be selling the old cattys too. I've just arranged to buy a retired background stamp from the BST forum for the first time. The seller was willing to ship to the UK and has been sooooo very helpful and friendly.