@trapped2019 - firstly I think you were right to pull out of the sale - if the vendor was willing to let you see the house in that condition, and for you to see the damage he was doing, imagine how much worse it would have been by the time you moved in! And I think you are right not to go back to the vendor either - why would you want to live in a house that you know has been full of dog shit, and damaged in the way you saw?
However, I do think your dh is wrong about renting being 'dead money' in this instance, as it would buy you some very valuable things:
1 - being able to complete the sale on your house - in the current market, having a buyer is not something to throw away - if you pull out of the sale now, who's to say whether you'd be able to find another buyer when you did find a property you wanted - especially with Brexit on the horizon.
2 - you get to sell now before any potential financial crisis after Brexit, which could have a negative impact on house prices.
3 - you could get away from your current area, which you hate (rightly, by the sound of things), and into a better area where you will be happier and feel safer.
4 - you could rent in the area where you want to buy, and get your child into your preferred school.
5 - you can take your time finding the right house, not just any house, whatever the condition (any port in a storm).
6 - when you do find a house, you will be cash buyers, chain free, which makes you very attractive to vendors, and might enable you to negotiate the price down - which could negate the cost of having to move twice.
And as others have said, as long as your rent and mortgage were broadly the same, you wouldn't be paying out more on a day to day basis - the main extra cost would be the second move (if you couldn't offset it by negotiating a better price when you buy), and even if you couldn't offset that cost, wouldn't it be worth it to buy yourself all those advantages I have listed, especially the peace of mind of living somewhere you feel safe and happy?