we had a 5 hour delay last year so we booked it there
did not have to book it before hand
best money we ever spent
you get free tea ,coffee ,soft drinks and biscuits plus two Alc drinks
there was free internet , Bar with a very freindly barman from France ,tv room with large TV plus lots of DVD's
Playstation room for the kids or adults . Kids toy room with soundproof glass door so you can see them but not hear them Great
so a nice time was had by us all
until we landed in Gatwick to find that we had missed our other flight home (Ryanair) and were put on standby Four flights later we got on
So Bewear
give your self plenty time inbetween flights if you are booking yourself