I've had success with taking this approach with Virgin Atlantic - no hassling, just explicitly asked for a manager to listen to the call, and I got my money promptly.

BA's attitude really stinks. And by BA's attitude, I don't mean the front-line staff, I think many of them genuinely want to help, and want to do the right thing for the customer. But management knows it needs to comply with EC261 and knows it must be equipped with the systems to accurately calculate and efficiently provide the refunds customers are entitled to, but they choose to do it in a way that suits them and definitely not the customer.

It might not be obvious to many posters on this forum, but for some people, a £10 or £20 loss is too big to be written off.