You have answered your own question, it is a dodgy poll.
You cannot compare the official referendum, and a voluntary internet poll in a newspaper. For a start, the samples will be very magnitudes different, and secondly, a newspaper will have a political balance, so readers of that newspaper are not a genuine political cross section of that area.
And thirdly, there is nothing to stop anyone from anywhere in the country voting it that poll, and voting multiple times.
The Express has been trumpeting the merits of Brexit though, so that it's their readers who've come out with this result is, perhaps, a slight embarrassment. But no, I wouldn't read too much into it. Possibly was just hijacked by Remain supporters?
///As I've said before on here, I didn't vote in the referendum///
You had the chance, you didn't take it for whatever reason, I suggest you thought you were above it all. If you now do not like the result you only have yourself and those of a similar mind to blame.
I agree that these sorts of polls are hardly scientific, but there does seem to be a bit of a pattern. And is it really only the "Remainers" who are motivated enough to respond in great numbers? Even if that were so, it would in itself be intertesting.
I don't think these self-seleted polls can be relied on much - though of course the referendum itself was self-selected. None the less, it makes sense for a nwspaper to find out periodically what its readers want, and this appears to have surprised them.
As the link explains however this paper carried out a similar poll in March which was the first to show people on the Staffordshire area favouring Brexit. And 78% of the return this time were postal respondents.
I voted out and would do so again. Polls are a waste of time. Look at the last lot in the USA. Here as well, they try to influence voting, slanted opinions, corruption personified.