I think it took me about 3 hours as I remember- but like you I would have had interruptions - not from a 6 week old baby, but from 3 18year old cats!
You can dip in and out of it, but as I dont trust technology to crash on me I printed off the questions and handwrote them, then went back to answer them- if that makes sense? only 2 log ons then. this also gives you a chance to research the bits your not sure of.
i did shred the questions after though- not that they're the same evertime but you cant be too careful.