This thread has made me feel so much better after I day of wondering if I did the right thing.
My Qatar flights BKK-DOH-AUH in First were cancelled and when I called BA this morning they offered me BKK-LHR(overnight)-VIE in Business (amazing they agreed to VIE!). I had a second Qatar booking from AUH-DOH-VIE that I could have cancelled to get my 12,500 Avios back on that booking. Eventually I was rebooked with the 2 bookings connecting at KWI instead of AUH.
Although I would have got Avios back, I couldn't quite bear the thought of replacing QR First with BA Business....so I'm so glad I didn't!