Why oh why do people do this to their garden voluntarily?!
Unfortunately enthusiasm beats common sense for all of us sometimes but there are a lot of people who garden without reasearch or reading a book/looking on the web, or even reading the label on the plant! Also people move houses. Your plants sound like at some point there may have been a gardener living there, but after that....? I left a lovely garden which I have heard since has "gone a bit wild".
I have Borage growing in mine. I also have a patch of Nettles - for butterflies and fertiliser - and some Wild Garlic - for insects - but I keep them under control (sort of )
I'm currently fighting with next door's Blackberry