No, you've missed the point, ITV & BBC cannot announce the result of the exit polls until 10pm. Upon the stroke of 10pm the networks can lead with these exit polls and predict the result.
:-(
A former member
Alright, not quite related to exit polls, but I quite like the election system here in Greece where it is _illegal_ to publish/broadcast _any_ opinion polls pertaining to the elections in the couple of weeks before and right up until the end of voting on election day.
Totally unlike the completely bizarre situation in the States where, as polling stations close on the East coast, exit polls from these are made available to the public - way before those stations on the West coast close.