Vauxhall Corsa won,t turn over

Cant understand post .You say pistons are working freely and then say car wont turn over .Car must be turning over if pistons are turning .You also say starter is o.k but not turning flywheel .Is starter meshing with flywheel ring gear or just spinning on starter pinion shaft ? If overheated and depending where head gasket gone , compressions may be knackered on a couple of cylinders.Could have also done rings or engine could hydraulic if water in sump .

hi, will try and clarify my original question, i have taken plugs out and pushed car in gear and all pistons moving freely. but when tried to start with key nothing, have taken starter off and tested , have found it to be spinning freely and shooting out to engage flywheel.i realise after overheating there could be a compression problem but am puzzled as to why it wont start on key. my next option is to tow start