The CO elite line informed me that Intl Change fees are $200 per change.

I have 2 BF tickets to LGW for July in R class. I had to change the return one day because of a change in ground schedule. The change for those tickets was $300 per ticket. It appears that the change fee depends on the class of service as well. However, the difference between R and Z or above is at least several thousand dollars per ticket, so I am still doing better with the discounted BC tickets.