So after filling a few skips so far and being told "no plasterboard", the penny only dropped that this might be difficult stuff to get rid of at the plastering stage. We have quite a large house so generated quite a bit of scrap, especially the rooms in roof where there are lots of triangular sections. Turns out that the local skip firm will do a plasterboard only skip but at an increased cost to normal to cover the additional landfill cost. I got a 4.5 yd for £265 inc VAT (Berkshire)