Just tried it out for the first time the past 4 weeks and it has certainly made the broad beans, peas and onions roar away.
I just went out walking with a green waste council bag as a receptacle and cut a bagful from various woods. Then I stuffed a Poundland big pot with no holes in (which I thought was useless for growing things but becomes great for preparing teas) with nettles, filled it with rainwater and left it to brew for 4 weeks. Then I filtered it 3 times through a kitchen steamer pot with holes in and stored in old olive oil jars, wine bottles etc. I used it to date twice at a 1:10 dilution the day before heavy rain was forecast. I wouldn’t guarantee anything yet, but it certainly seems to have increased the growth rate of the broad beans especially. We’re in early May and they are 4 – 5ft tall and are showing pods now after early flowering through April.