Just signed up for O2 and handset was delivered today (21st), as
agreed at time of order. They've already generated my first bill (they
don't hang about) and they've charged me in two lots;

a) from todays date for a full months line rental.
b) a pro-rata amount for line rental for yesterday (20th)

Is it usual for O2 to charge people for service before they've even
received a handset to use that sevice on?