Yes, it works very well for attaching curtain polesI've solved the problem on similar walls by attaching a rectangle of wood to the wall using a whole bunch of screws, and then attaching the 'whatever' to that bit of wood.
you can tell if they are thermalite if they are a very light bluey grey , maybe got wavey lines on them and if you throw water at them it sucks up like a sponge . if they are then the ply method sounds great as they are a pig to get a fixing in - lovely to lay - you can rattle them in even cut them with a hand saw but they are horrible to live with - no fixing strength and crack everywhere - we now have to put expansion joints everywhere when laying them to try and stop the cracking ! worked on one house where the sparky was leathering the wall downstairs and other side of build and i could feel the wall i was working on moving
blitzing a hole for a load of cables- he took a whole block out for a hand full of wire , the man was an animal who didn't own any hammer smaller than a 4 pound lump hammer - dont even think he used a chisel - dont think he had your finessedunno why he was leathering the wall, as you say its soft and e3asy to cut. used to love final capping over cables on thermalite, toffee hammer to drive the clout nails in.
thermalite blocks are so porous that you may end up pumping a lot of resin in to the holeIf you want to fix something big, use resin anchors. Don't foget to blow out the dust before squirting in the resin ( not into your own eyes! )
http://www.screwfix.com/p/no-nonsense-polyester-resin-175ml/53359
electricians have a rule book that says 'every hole to be drilled with a hammer'dunno why he was leathering the wall, as you say its soft and e3asy to cut. used to love final capping over cables on thermalite, toffee hammer to drive the clout nails in.
nah thats clankies and plumbers. when i started my apprenticeship the clankies had rawltools for forming screw holes as they couldn't be trusted with a power drillelectricians have a rule book that says 'every hole to be drilled with a hammer'