I have never had a cambelt failure, but have suffered 2 auxiliary belt failures, both due to tensioner pulley bearings stiffening up. Not catastrophic failures, but very inconvenient. Following advice from Nick W, I now take the pulleys off occasionally and grease the bearings.
had a cambelt let go on my bro's old astra f ,had to drag him off a live lane of the A38
,waterpump u/s ,bent 2 valves and broke several rocker arms ,replaced the bits, engine ran sweet till tinworm ate the cills
also recently had a waterpump seize on the in-laws sierra, took the belt out ,bent a few valves ,bummed a few hydraulic lifters ,replaced the lot (including head refurb VS oil seals etc) ,less than £100 in parts ,engine runs sweet, and £100 is what the local garage offerrd them for the sierra scrap