You can use any e-mail address. I received the code in about 30mins. **note** you need to make a UK within your PS3 with any UK address (I used a hotel's address in london) put the SingStar game in your system and log in using your newly made UK profile enter the code in the Singstore and your good to go!
Good Luck and happy shopping!
I just tried this one http://www.xboxliveuk76.com/ and I had the Card Number e-mailed to me within 30mins.
It was about $33.00usd for a 20 Uk card. I was able to Download 20 songs from their store with it.
I will be getting more from this seller!