vauxhall corsa- wont start !! help... :(?

my corsa 51plate 1litre wont start, had to have head gasket n raidiator replaced ever sinse then car hasnt started properly, was told it was timing chain and the man was meant to get bk to me never did, been driving it around for a few months no problem just not starting striaght away, now it wont start at all. Oil, water fine got petrol so that fine, Checked spark plugs they fine... Ne ideas of why it wont start.. its stuck outside my mates house till i can get it moved. :(