The YouGov link is an article, as is the Independent. They interpret the figures.
The Lord Ashcroft link is interesting:
- A majority of those working full-time or part-time voted to remain in the EU; most of those not working voted to leave. More than half of those retired on a private pension voted to leave, as did two thirds of those retired on a state pension.
- Among private renters and people with mortgages, a small majority (55% and 54%) voted to remain; those who owned their homes outright voted to leave by 55% to 45%. Around two thirds of council and housing association tenants voted to leave.
- A majority (57%) of those with a university degree voted to remain, as did 64% of those with a higher degree and more than four in five (81%) of those still in full time education. Among those whose formal education ended at secondary school or earlier, a large majority voted to leave.
- White voters voted to leave the EU by 53% to 47%. Two thirds (67%) of those describing themselves as Asian voted to remain, as did three quarters (73%) of black voters. Nearly six in ten (58%) of those describing themselves as Christian voted to leave; seven in ten Muslims voted to remain.
- The AB social group (broadly speaking, professionals and managers) were the only social group among whom a majority voted to remain (57%). C1s divided fairly evenly; nearly two thirds of C2DEs (64%) voted to leave the EU.
From the Electoral role how can they find this out? I certainly didn’t give anyone any of that information.
So they asked a sample of people and then extrapolated the answers they got to apply to everyone.
Let me give an example in case you never watched Yes Minister.
In Leeds you ask a group whether they work or not then whether they support Leeds.
From the results you will probably be able to say that more people in Leeds support Leeds Utd than work.
For Man Ure you’d probably have to do it in London

Polls depend on who you ask and what you ask.
The only Brexit Poll that I trust is the one that polled nearly 34m voters, not just people but those eligible to vote.
If you compare the figures in the polls posted they are quite different so a judgement has been made.