Q.Bindweed or Japanese Knotweed
Just moved to Kent this month. Suddenly vine like plants appearing in bare earth. Area is about 20′ x 10.’ Obviously, previous owner tried to eradicate. Some stems appearing in grass too. Also in next door garden. Very worried this could be Japanese Knotweed.

I have to admit - it does look a lot like japanese knotweed. Here is an article on japanese knotweed control that will help you:
https://www.gardeningknowhow.com/plant-problems/weeds/controlling-japanese-knotweed.htm