2005 Renault Espace Big end bearing

I have a 2005 Renault Grand Espace Expression 1.9dci with 102,000 miles. It has been well serviced, infact serviced at a higher frequency than the minimum requirement, and always by the Renault dealer that sold the car new to me. Recently, for no apparent reason the big end bearing went, and the Renault dealership wants €7,500 for a reconditioned engine. I have asked how this could possibly happen given that the car is well maintained and was not low on oil. The answer has been 'just one of those things'. However, any mechanic that I have spoken to has said that there is always a reason. I went back to the dealership to ask the question again and they tried to find a reason in my service history (i.E. If I ever had someone else service the car. But of course they were never going to find an excuse there because they have done all of my servicing, and I have never missed one).

I have always used Renault for the servicing, paying far over the odds so as to avoid anything like this. The irony is that had I used a back-street mechanic for all the work carried out (and boy there has been a lot!), I would have enough saved by now to pay this bill!

What should I do?