Got the EPDM on layered: supplied 19mm T&G, VCL, 50mm celotex, 11mm OSB then 1.2mm EPDM on that. Thanks to Bodgit Jnr for his help, couldn't have done it on my own. The EPDM weighs a ton. Managed to put the EPDM on the "wrong way round"; both sides are identical other than one side has some faint blue writing which can hardly be seen. Its facing up, only noticed/thought about it once one half was laid Struggled to get the screws to grip in the T&G: with 19mm T&G, 50mm celotex and 11mm OSB (80mm total), bought 75mm screws as didn't want them to start poking through inside. Towards the end I countersunk the OSB a bit so a bit more thread would grip, should have done that at the beginning. Had loads of glue left over, used 5l + a bit of the 2.5l water based adhesive, and probably not quite half of the 2.5l contact adhesive around the edges. It does stick good, it ain't coming off. Need to cut the edges and finish it with eaves boards, all in good time. Its flippin hard work, took all of Sunday until about 8pm, crouching down to screw, glue etc. Once the OSB was on I used a reciprocating saw to cut the edges to size, its rather rough round the edges but it'll be covered by the EPDM and eaves boards. Used the supplied 50mm tantalised foundation timbers around the edges of teh roof to make a perimeter for the celotex to sit within, those on the long sides I cut at 10 degrees so the outer edges and eaves boards will be vertical.