Capetonian,
I am truly sorry for the experiences you've had with us re-your son's lost pushchair. It was nice of you to write and thank the member of ground staff who was incredibly kind to do what she did. Equally, it would also have been nice for her to have seen the nice gesture from yourself in taking the time to write.
Perhaps in the future, it may be an idea to write to Willie Walsh himself in extreme and exceptional cases. Based on personal experience where a customer on one of my flights wrote to him directly very recently, he does read the letters which do get then get a response as well.
Now please don't all rush to write to Willie Wash at once!