When it comes to it, don't be afraid to chase up your documents, I've found OFSTED to be really disorganised! I was waiting for my certificate and when I phoned them to see where it was they were arranging a pre-registration visit for me instead of sending it out.
I explained that I didn't need a visit as I'm not on the Early Years register as I'm only looking after over 5s. They toddled off to check, sounding thoroughly confused, then came back and agreed that I didn't need a check! This was 2 weeks ago and still no certificate - aghhh!