Hello
I was interested to read the comments on getting started on a large area of possible couch grass. I wondered if you had thought of using a tarpaulin which is a lot cheaper than Mypex. I had a large extremely over-grown allotment as mentioned on previous posts and found Mypex was going to be a bit expensive but discovered you can buy tarps which are cheaper. I managed to buy two in a deal online and covered the lower half with just tarps while I worked on the top half using the no dig method and manure. I ran out of steam to get more manure for the lower half.
After some months, I turned back part of the tarp and thought it had not worked as the grass was long but as i went to pull it, it just came off with no roots attached. I think it had outgrown itself under the tarp. There is no sign of re-growth. If you have the energy and enough manure to put on, covering with a tarp should work well.
Big D