I found the answer re:£25 charge for changing - the agent was applying the post 16 Nov fees - according to the FAQ from Nicci - the agent seems to think I booked my ticket in Jan
Do old tickets retain the old policy of free online date changes? Or does the first date change trigger the new fee schedule for subsequent changes?
Reward bookings made before 16 November can be changed under the previous rules with any applicable fees either online or offline. This will apply for the whole validity of the ticket regardless of whether single or multiple changes are made.