I used 65 mm aluminium clout nails (flat wide head) to fix the batons. I think traditional slating and tiling was done with copper clout nails which you can still buy but aluminium is much cheaper. The idea is to use a metal that won't rust. I found the best place to buy all this stuff is a dedicated roofing supplier. It's a bit too specialist for a general builder's merchants.
July 2009: The batons were fixed with 65 mm aluminium clout nails. The lines and spacing of the batons dictate the final look of the tiling.
It's important to set the first baton in the correct position so the first row of tiles overhang the gutter by 50mm. Once this is in place it's just a case of spacing them up the rafters. I wasn't entirely sure what to do at the top by the wall but my spacing arrived naturally with a gap for the nibs so I just let it end where it ended. The membrane is also taken 50mm above the battons where the lead flashing comes over the tiles at the top.
July 2009: You need to overlap each strip of semi permeable membrane and allow it to sag about 10 mm between the rafters.
July 2009: The finished batons with the semi permeable membrane overlapping 50mm where the lead flashing will be installed.