Exercised the franchise here in West Oxon as lunch time. Steady stream of voters. LibDem and Labour tellers outside cheerfully cooperating on taking poll card numbers so as not to hold people up. Tory teller sitting on his folding chair six feet away, looking down at his clipboard.
No, they're from party organisations. They go round chasing up people they canvassed who said they would vote for them, and haven't. You don't have to give tellers your number, but you may get a call in the evening to vote. It's kind of in your interest to give it to them.