sorry i didnt really say but the cambelt didnt break clean, it was still intact when i went in. I guess it just slipped half off or something - does this make any more sense now? perhaps it continued going around after it initially failed, bending more valves. The mechanic did mention, it would have been better if it had just broke.
When this happened I was just driving along in 3rd or 4th gear, doing around 3.5krpms - nothing major. It simply cut out, there were no loud bangs or scrapes which is why I was very surprised to hear there was actual damage.
Thanks