Thanks for the feedback Mike.
In case it ever helps anyone else it’s possibly worth pointing out the confusion on the TfL website when applying for the 60+ Oyster. They say you can apply two weeks before your 60th birthday. I tried 14 days before, I tried 13 days before – to no avail. I called TfL and they told me that it’s actually 10 days before. I tried 11 days before and it worked.
What is stated on the website and is actually true is that you can use the card as soon as it arrives – you don’t have to wait until your birthday!