Agree, getting the cashback is a bonus. I used TCB when switching bank accounts, car insurance and recovery and the "bonus" would have been about £350. It was all declined. These were the best/cheapest for me anyway but I was pretty grumpy and when I asked why just got the standard cut and paste responses. Didn't bother with TCB at all for a while and then decided I'd use them and just be grateful for what I got. I do think it reflects badly on big companies when they offer cashback and then appear to find ways of weaseling (if that is a verb) out of paying.
Phew, feel better for that.
On a more positive note TCB have successfully pursued untracked cashback claims for me. I recently got 62p from SW Trains from 2012. Yay. What I have discovered is that AdBlocker seems to be the culprit when my purchases don't track and I try to remember to turn it off while making a purchase.
I did question the declined £7.87 from BA but too soon for a response yet.