Posted: 30/05/2014 at 15:50
That looks like Hypericum also known as St John's Wort. It's frequently planted as groundcover as it requires very little looking after - however I think it'll take some digging out to get rid of it. I would just get stuck in and dig and dig - I don't think it'll go too deep.
Then leave the area for a while and see what regrows - you can then paint a brushwood killer onto the leaves of any new growth.
I don't imagine that you'll be replanting that area until this time next year, but it's as well to do the job properly.