I expect the exit poll yo be released shortly after 22:00, perhaps 22:15 or so. That'll give a pretty clear picture as to how the night will go.
The first result will probably be around midnight, usually from 23:45. The first expected calls ar2 from pretty key seats that were largely leave but Labour marginals. After the first 10+ the picture will be clearer. Depends after that if you still fancy watching haha