If it's the 8v engine, then cambelt kit can be replaced for less than £100 inc cambelt kit from a none vauxhall garage, change thermostat whilst your on.
If it's the 16v engine, then probably cheaper to change engine or get rid of car. 9 times out of ten major engine damage will of occurred when belt snaps.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.