Ah ok. I didn’t know about the restriction on Advance tickets because I haven’t tried to buy one before with the Oyster 60+
It’s true that I always assumed with my pre lockdown Gold card that I couldn’t combine it with an Advance ticket because my Gold card was only zones 1 to 3 so didn’t cover much of a distance. I only got discounts on Network South East.

I suppose I will have to compare the cost of an off peak from Surbiton to Bournemouth with the cost of an Advance from London Waterloo.
I didn’t actually mention the term Advance tickets when I rang National Rail. I only said I needed to cover the route beyond zone 6.

Yes. I first wondered about this about a year before I reached 60. There is already inaccurate info on the 60+ web page. You now can’t apply 2 weeks before. I tried and was blocked so I rang TFL and was told that it was now 10 days not 2 weeks. I tried again 3 days later and it worked. They still haven’t corrected that.