vectra 1.7 td running hot?

I've got a P reg vauxhall vectra 1.7 td (izusu engine) which just resently has started to run hot, (temp sitting at 100c) the cooling fan cuts in and brings it down to 95c, iVe had the car for 3 years and the temp has always sat below 90c even in the summer. Mecanic's who have worked on my car in the passed have said what great engines they are, if you dont over heat them!!! As you can imagine i'm quite concern, any idea's?