Posted: 20/08/2017 at 18:31
To be honest, if you want good crops you need to fork over the whole area and add plenty of well rotted manure and garden compost to make sure your new fruit trees and shrubs have the best conditions for growing well and producing good crops so you may as well just get on with it and remove as many roots as you can.
Neither bindweed nor couch will be very much weakened just by covering in my experience. You need to spray or hoe the top growth and leave it to die and dry completely then burn it or bin it but not compost it.
As Dove says, you then need to spray any new growth that appears with a systemic weedkiller. I would suggest one for brushwood as bindweed and couch both have very strong root systems and need, in my experience, several applications of glyphosate to kill them.
There's time to have a go at this now, assuming you get a mild autumn but, as Dove says, the best time is spring when they are in active growth. You could also try covering the entire area with layers of cardboard in November. This will stop any new weed seeds germinating and it will also rot down into the soil and improve its structure so it will better support your fruit once you've cleared the perennial nasties.
If you don't want to be bothered with all that, just use cardboard anyway or weed proof membrane available from DIY stores and garden centres and plant through it and finish it off with a 2 or 3 inch layer of chipped bark after you've watered all your new shrubs and trees in.
Be prepared to watch the planting holes like a hawk and pull out all unwanted weed growth the minute you can grab hold of it and before it swamps your treasures.