We're up against a greasy little bag of RNA that doesn't give a shit whether we've fled London for our second home like Prince Charles or whether we're rescuing our young adult children from what is probably going to be a risky and horrible few months in London for them. The virus doesn't care whether you feel guilty or not, it doesn't care about the spirit of the guidance. If it gets a chance to jump hosts and spread itself then it will. That's all.
This is why we are fucked. From a human point of view, who wouldn't want to rescue their child in such circumstances?
London is a seething petri dish of infection. Some other areas of the country are not (yet) and still have a chance of avoiding catastrophic overload of local NHS resources and rapidly escalating numbers of deaths.
North Yorkshire is huge and has 75 confirmed cases. They will not be spread evenly. I haven't looked but I bet you half a bog roll that the cases make up one or two clusters in towns which could still be contained if the will was there. London is not huge and has 5299 confirmed cases. It's an extremely interconnected city which means the cases are fucking everywhere. And your daughter lives in a shared house which greatly increases the risk that she will come into contact with it.
From a public health point of view it would be best to support your daughter to stay where she is and prevent the spread to areas that are still only minimally affected or may not yet be affected at all.
But if nobody else is bothering to prevent the spread then will it make any difference whether you rescue your DD or support her to stay where she is?
If you decide to go and get her then 7 days isolation is inadequate and not in line with WHO advice. Ideally she would spend 14 days in strict isolation where she is (but this will be extremely difficult in a shared house) before any rescue attempt. Otherwise 14 days strict isolation at your home and all of you should isolate because she'll have been in a car with your DH for a very long drive.
I'm sorry you're facing such a horrible choice and I don't know what you should do 
