On the roof we have thirty 58mm diameter evacuated tubes.
The roof faces a few degrees south of south-east, so not perfectly ideal but it does get the best of the morning sunshine. The silver thing sticking up at the left hand end of the manifold is the automatic air vent which automatically clears any air trapped in the panel. I didn't fancy drilling big holes in the tiles, hence the loop of plumbing under the eaves (partly done with flexible stainless steel hoses).
TheSolarShop sold us a kit of six roof screws that are long enough to go right thru the tiles and screw into the rafters. Actually it is easier and stronger to fit noggins between the rafters and screw into those. That way you can drill thru the roof, then poke the screw thru and then fit the noggin in the correct place. Use a masonry bit but not hammer action, plus a bit of wood to stop you smacking the drill chuck into the tile when it finally breaks thru. The protruding end of the roof screw is a male M8 thread that you can then screw the panel frame down to.
Here's Julie marking the positions of the roof screws with chalk:
Please note: We are experienced cavers and climbers, don't clamber around on the roof unless you know what you are doing!!