The best way to get rid of couch grass is not to worry about it. Don’t dig, cover with an organic mulch and it will grow into it. Couch grass is usually shallow rooting so after a time you should be able to pull it out.. It will take acouple of years, but if you keep pulling it will disappear. If it breaks when you pull it will grow a new leaf but will be weaker. You could also rotovate the patch and as long as you dont walk on it, each little root will grow and if you keep pulling as soon as the shoot comes through the little roots wont be able to take hold. But for this you need to be able to spend the time to stop it taking hold again.
Pete