Hi Charles and Bluebell
I am in a similar situation with what was a very weedy plot which I have covered with about 3-5cm of muck and then covered with mypex or plastic sheet.
My question is about whether the mypex will be sufficient to stop greening of the potatoes as it will not be practical to earth up.
I plan to burn holes at 60cm centres so the sheets can be used for potatoes, brassicas, courgettes, squash etc. I think the 60cm spacing, giving 2 rows across a 1.2m ‘raised’ bed, is quite adaptable and could be used many times, particularly if my rampant bindweed is slow to clear!