Polls close at 7pm except in larger cities, but counting of votes start at this time. It's forbidden to leak the results until 8pm, at which time the sample is large enough to give a precise estimate, unlikely to move by much.
Since the polling booths are now closed (it is 8:30pm in France), these exit polls have been published. That is what the Beeb article is based on.
More importantly, at which time all booths are closed.