It's midnight, so may as well get this ready.
Polls open at 07:00 BST and close at 22:00 BST.
First results are usually announced by about midnight, the election is usually called about 4 AM and all results are usually in by 8 AM Friday.
I'll be following the BBC as they are more cautious in confirming votes and results. (Their charter requires them getting the results and current counts directly from the various Returning Officers, not some rando poll worker). This means a bit of delay, possibly, but a more accurate tally. I'll post the link once they finalize which one they are going to use.
A few facts for the ones who watch but don't really know the systems fraud prevention methods:
1/ It is a first past the post system. The leader of the party which gets 50% +1 of the MPs is the Prime Minister. Legal challenges for individual seats can and do happen, but they never delay the result.
2/ It will seem slow. We do NOT use electronic voting machines. Everything is pencil and paper and hand counted (three times).
3/ There will be no boxes of ballots "found." All ballots from each polling station are transported by the police directly to the counting office. Counting doesn't begin for a station until all boxes are accounted for.
4/ Postal votes are counted at the same time as the personal votes. A person who has requested a postal vote will be turned away from the polling station.
5/ There are no bussed voters. You vote in your assigned polling station, by post, or you don't vote at all. Polling stations are based on the current electoral register, which is updated once per year (failure to send in the update form lands you in court!).
6/ Each polling station recieves exactly the number of voting slips as there are people registered to that polling station plus 5 or 10. So if you are going to make a mistake, make it before 8 AM, cause you are out of luck otherwise! The blank voting slips are also counted and tallied against the number of people per station that didn't vote. Any discrepency triggers a recount for that station and the opening of a police enquiry.
Hope that helps some! We've been doing this a while and the system is pretty airtight now.