I've got mine on Tuesday! Ofsted phoned on Friday afternoon so at least I've not had too much time to worry about it - not that I am really, I know my paperwork is all correct and I've done appropriate courses etc it's just that anxiousness about the 'official' side of it.
I used to be a cm, but stopped just as Ofsted started upping all the paperwork that needed doing - so the inspection lasted about 1 - 1½ hours. I hear now that they can take 4-6 hours for cm's 
If you've had an inspection as a nanny, how long did it last? Nice sounding lady on the phone, she said it wouldn't take too long, but how long is not too long? Also, what kind of questions will they ask me?