I think this should be "..almost 4 in 10 Mumsnet users WHO RESPONDED TO A SURVEY say they have been in a controlling or abusive relationship"
It was a self-selecting group and the results have not been weighted.
While I think it's absolutely right to raise awareness and get people talking (and doing something) about coercive control, I think it is equally important to report statistics correctly.
Also the URL www.mumsnet.com/relationships/coercive-control has a in the opening paragraph (controlling or abusive relationship with a partner" but there is no corresponding * to explain what this means on that page.