Orange define peak times between 6pm and 11pm. Peak times are when a majority of users are connected to their service.
In their T&C's they mention p2p software usage during peak times, so rather than push it I simply dont use p2p software during those times. It doesn't say you cant download between those times though.
Orange say "Unlimited but subject to fair usage". In reality the word "Unlimited" is incorrect as the fair usage policy seems to be 50gb per month which is easily enough for most people. With 50gb of bandwidth a month you could download a full CD's worth of data every day and still have over half your bandwidth still to use.