...saying that though, the £20 6gb bag is unique offer that can't be found anywhere else as far as I'm aware. It is very good value for money considering what you'd have to pay elsewhere if you're a heavy user and you need to "top up"!
I think I've prejudged a little in my initial comment (sorry giffgaff) I'll stick with it, make more speed tests in a more scientific way and post my conclusion later down the road.
