00 1.8 Broken Cambelt - richm

Hi,
I need some help here please, my son has a Bravo 115HLX 1747cc Bravo & the cambelt snapped. We have had a mechanic round to change the cambelt & he then told us that it needed to have new valves fitted.This so far has now cost us £430.00 He is now telling us that as the car does not start/run (thru no fault of his as he doesn't have diagnostic facilities) it now needs some kind of sensor to get it going again,

Can someone please advise, have we been ripped off????? Is the sensor needed or has the guy mucked up???

Please help if you can
Many thanks