It actually isn't valid to lump three different viewpoints in as one by any reasonable and logical basis. For example, Don't Know does axiomatically imply disinterest or don't care.
If your assertion were true, Ashcroft would have stated precisely what you assert. But he did AND does not. The fact remains you offer no evidence to support your argument and, where some is offered, you simply misrepresent the data to suit yourself.
Very curious how you don't even apply the same flawed argument in relation to Scotland. The percentages and, thus, the viewpoints of the English population is highly similar to that in relation to Northern Ireland.
It helps highlight your flawed logic.
Final word to Ashcroft AGAIN:
"....only a handful say that if either voted to leave the UK they would be happy to see them go. Of those who say it is for Scotland and Northern Ireland to decide, a large minority nevertheless say they would be sorry to see them leave if they chose do so. This means that, overall, most English voters would rather keep the union together if it were up to them – though they recognise it isn’t up to them."
Ashcroft is an experienced pollster who knows how to correctly draw conclusions from his own poll.
You, on the other hand, simply aren't experienced nor know how to correctly draw conclusions from polls.