My train from Paris to London was cancelled, I can’t change the ticket because I can’t travel the days before, and so I have to cancel my hole trip to London…

Refunding for Paris-London was possible, as the train was cancelled (the reservation was made with SNCB and no problem).

So, what about the way back, London-Lille ? Yes, the train is not cancelled, but… The reservation was made with eurail, which says “No refund”.  

Does anybody has any idea for how to get refund ?