i know what you are saying, had a cliteron c3 recentley that was trying to fire it had stripped 8 teeth of the belt!

the guy saying above about changing the comlete engine is wrong imo, the cost of a new second hand engine plus fitting would well outway the cost of repairing yours if you or a mate are half decent at wielding spanners you could sort it diy, zetecs usually bend at least 2 valves ive personally not known one bend more than 5 rough prices would be
pressure test and skim on head £50 (may not even be neccesary due to just being a snap not headgasket failure but i myself would do anyway while valves are out)
new top end gasket set £30-50
new valves (5 or so) £30
cambelt kit £50-60
oil plugs etc £30
so roughly £220 worst case
these are a really easy engine to work on so armed with a haynes manual you cant go far wrong mate