Not so, at least in UK. I just buy a non-O (single or multi-entry). Enter for 90 days. If multi-entry, repeat for up to one year. No insurance or deposit of funds required. Just need to show pension statements and be over 50. Easy, really.
It's also possible to get a multi-entry Non-O, which would mean he could just leave the once, without having to worry about 60+30 extensions on the METV but that may not be cost-effective in terms of fees.
I spend 6 months in Thailand (in two blocks of 90 days) and 6 months in UK, each year. I've tried a variety of visas over the years but the easiest is now the non imm-O based on being over 50 with pension. Only significant requirement is to show pension statements, no proof of insurance is now required.
In fairness, this was the first time I'd used the Airport office. Previously, I'd always used Promenada, in CM, which never asked. Nor did the Phuket office last time.