Plant taking over my garden

You could clear areas by leaving thick black plastic or old carpet down for about 18 months. It won't exactly look like a show garden though.

 

I had it, it took me 3 years to dig it up, the roots can go down deep, the first thing i did was to dig out the mass and as much root as you can, then keep the soil loose and keep digging,as soon as you see new growth dig that bit out,if the soil is loose it comes out easy, mine was under a Berberis Thumbergii hedge so not a nice job, but i'm now free of it , if you dig it up don't but it in the green waste bins as it may get recycle into compost