I am not sure if this can be done or not, I suspect not when I can not find anywhere to do it online & searching on here I can not find it answered.

I currently have a redemption flight booked LHR - CPT and when I booked it there was no availability on the GLA - LHR flight we wanted so booked that as a cash booking. (we are flying out for our wedding so we had to book the LHR - CPT flight as soon as we set the date as could not risk waiting to see if we could get the GLA one at a later date)

There is now redemption on the GLA - LHR flight and I am wondering if I can add that to my original redemption booking. I know that I am not likely to get anything back for the cash flight and accept that, it is going to be so much easier not to have to get bags back at LHR and re check in etc (and will have my mum travelling with us who is on a through ticket for the route)

I am BA silver if that makes any difference