Thank you for all these answers. I know Mulfab and 2 friends have replaced their radiator with a Mulfab without any concern at the moment.
I have asked advices because a new friend has just bought a 2002 tourer and his radiator is leaking, the same than indicated in the link above(SERCK). The tourer has only 7000 miles and the tag on the radiator indicates a date 30 sept 2013. The radiator is quite new and seems externaly completly new, but has 2 small leakages on the right side, top and bottom.
It seems that people don't use a lot this make.
I wanted to know if this was a ponctual problem or a general quality problem. The price is cheaper than Mulfab which has a good reputation.