Just ordered one myself form these guys.
I was aware that they offer £20 to the person who refferred me.
I told them I didn't know this "persons" second name, and asked if I could forward their details at a later date.
They told me that this "person" who has ref'ed me, should call them and say "I referred <my full name>"...and they would get £20 when I've paid me first bill.
So, if you want to be that "person" and bag yourself £20, pm and reply here, and ill give you my full name and details.
Cheers, stu