It’s just me on the booking. I suspect Krisz is correct in saying that the change fee for CE is actually £100.

This is not the wording on the booking though. It quotes a £50 change fee when I click on the outbound economy sector. It also quotes £50 if I click to change the inbound CE sector.

However when I actually attempt to change the CE sector I’m charged the £100 fee.
I tested changing just the outbound economy sector and would have only been charged the £50 fee. Changing both sectors £100.