Miles More

Dear Forum, I have a 59 plated Citroen C5 Tourer, which has the 2.0 HDI diesel engine. I bought this vehicle as a year old ex-demo from a Citroen main dealer in Redhill. I have an airport transfer business based in Norwich, which takes customers to & from the London airports. I do around 70 to 80 thousand miles a year & mostly motorway driving. Since I purchased this car, I have had this vehicle regularly serviced by my local main dealer. My vehicle is at 226,000 miles and up to last week is still in fantastic condition & a good runner. I have had a previous C5, which I achieved 400,000 miles & therefore I know these Citroen C5 HDi engines are good for many miles. My problem is that as I regularly serviced my car with a Citroen main dealer, I thought that they should advise me or automatically replace the cam belt when required during the routine service. My cam belt snapped last week & it looks like it has damaged the sort of fail safe rockers. This job is still going to be expensive to put right. I asked the garage if they had replaced the cam belt at around 150k, which is when I have been advised they should be changed. There computer system does not show that they have ever carried out a cam belt replacement. Is it possible that a car can achieve 226k miles without a cam belt replacement? More importantly is my garage responsible for not advising me that the cam belt needed replacing?