The title of Barry's post suggests that he's trying to use AB as a matchmaking site! Having read his post, I'm still not entirely sure that he isn't ;-)
On a purely practical note though, where Government-imposed rules don't apply, the age for granting 'senior concessions' (if any are actually given) is entirely at the discretion of the relevant company or organisation. Many hairdressers, for example, offer a discount to people who are (or simply appear to be) over 60. I've been paying 'pensioner rate' since I was around 50, despite never having asked for it! (I've never heard of a hairdresser demanding documentary proof of a customer being over 60 and I've most definitely never heard of a hairdresser shifting the age qualification to get a discount in order to match the State Pension age!).
Similarly, I've never been asked to prove just how ancient I am when asking for a Senior Citizen ticket for art galleries, museums, etc.
If you want to buy your missus a little gift to cheer her up, why not present her with entitlement to discounted travel by rail
https://www.senior-railcard.co.uk/
or by coach?
https://www.nationalexpress.com/en/offers/coachcards/senior
Both National Rail and National Express still regard 60 as the qualifying age for cheap travel.