I don't think it's a lax of the registry office..
they checked my passport and visa and lots of questions were asked too. They almost didn't even registered us when Keith didn't bring his passport. Good thing he has driver's license with him showing his details and picture. It's obvious that I still don't have any proof of address at that time other than the mails sent to me of some magazine subscriptions Keith had for me and that Matalan membership. At that time the letter from the GP hasn't arrived yet too. So I think they can accept reasonable circumstances. My point of view only and that made everything easier for us.