The Apprentice wrote:
we can save double that difference every year with our plot and a couple of greenhouses
Problem is we already have been saving that

We've been growing our veg for years and there isn't another £4k p/a saving to be had
Even if there were, we aren't in a position to front up the necessary, nor are we inclined to line the pockets of a greedy barsteward.
I will reiterate my view that weeding is not always a good thing. Adopting permaculture principles (ie minimal interference) where you can is a sound and beneficial principle. In the wider natural world (except things like locusts) there is rarely a problem with pest accumulation. This is something we can mimic in our plots by allowing mother nature to carry on and working around her.
The principle of green manures that the apprentice touched on is a very sound one and has many uses.
I have used them as a part of a ground clearing/preparation process on many occasions and they really do work.
First step is removing perrenial weeds like bindweed, redshank, ground elder and the ilk (yes I am advocating that less weeding is more but I mean in the plot in general not so much in amongst your crops, perrenial weeds are a no no in crops) as best you can. You'll never do it in one hit but you can get 80% of them out.
Next, I cover the ground for a few months. By that I mean putting something like old carpet on it. This blocks the light out and further helps sort out the perrenials.
Then I would plant potatoes as a clearing crop to further help get on top of the perrenial weeds. You probably won't get a massive yield from that but it's not the point.
Then comes green manure. Red clover and the bean family will fix nitrogen from the atmosphere, into the soil. If you pull up one of these plants when they are mature you will see little white globules on the roots. That is nitrogen. Turn the crop into the ground and you have boosted the nitrogen content immensely. Some self made compost added at this point will further condition the soil, encourage worms and aid fertility.
From then on I'd be using green manures in the rotation. Once every four years I'd sow a green manure.
As the apprentice said, you can also use them in trenches when planting beans etc. Muck is the best for this of course but not everyone either has access or inclination to muck.