I picked up a couple of '4-way earthing blocks' from B&Q yesterday, similiar to the block in the diagram - £2.98 each (probably get them cheaper in an electrical wholesalers). Basically, they are blocks of steel, 50mm x 20mm with 4 pairs of screws in the top (like a solid metal version of chocolate strip if you get my drift) - but everything is commoned up, ideal for connecting lots of things together.