Originally Posted by JamieTC

'if done via BA.com as opposed to a travel agent - you can make a change like this without a change fee. However you would have to pay the extra on the extra leg, which could be very low (or could be otherwise).'

Just to pick up on the above, any Travel Agent should (I certainly would, and hope everyone else would! ), be able to void tickets on same day of issue and introduce that leg into the booking. And yes correct with the extra fee for that leg.

One of the benefits of dealing with a person, rather than booking through an online site!