To be honest, I probably would have asked the agent to escalate it to the duty manager. When the call centres themselves make mistakes, they tend to have "budgets" and a process in place for customer resolution. However, that has now passed.

I don't believe your requests are entirely unreasonable though I suspect whilst they might easily throw a generous sum of Avios, they might be more tight about the monetary aspect of it. I'd probably wait another week or so and if you still haven't received a response you could try tweeting BA and asking them to push things along? This has worked for me in that past.