Please help put my mind at rest. I've just watched an episode of Emmerdale, in which some of the characters are having a friendly game of Texas Hold-em. The flop in down, there are only two players left in the hand, player 1 checks, player 2 checks, then player 1 raises, surely the betting round is over when both players have checked, and the raise is void, as there is nothing to raise against, or have I got it wrong?
A betting round is over once all players in the hand have acted. In Texas Hold 'Em, the turn card should have preceded the next round of betting. What you saw on the episode was incorrect.
Yes, betting is closed for that street(flop) once it has been checked around.
Even if player 1 bet and player 2 called betting would be closed for that street.
If player 1 bet / raised that could be interpreted as bet / raise in the dark for the turn. You can announce check in the dark so you should be able to bet in the dark. There are some dealer on the site so hopefully they will chime in. Most likely the dealer would tell the player betting was not yet open and player could say that is my bet on the table once betting is open.