My colleague left his UBS account open for almost a year after leaving Switzerland - the monthly fee went up to 30CHF to cover it and AFAIK they were fine with it and he'd definitely handed in his B permit when he left. Maybe rules have changed recently as this was in 2021 to mid-2022 when he sent his pillar 2 cash back when the rate was much better.
Alternatively, OP could just deposit his/her pension directly into a UK bank account denominated in CHF and save him/herself the hassle and cost of maintaining a Swiss account as a non domiciled person.
Something to look into, thanks.
“Citizens of the EU, Norway, Iceland, Liechtenstein and Switzerland who move to the UK from 1 January 2021 for more than 6 months will pay the immigration health surcharge as part of any visa application.”
That would giove access to the NHS (depending on Nickj’s spouses citizenship), but it is all spelled out here
About 3 years ago I was considering taking a break with Switzerland. IIRC, my bank www.bcv.ch allowed to keep the account for a fee of 40 chf/m for non-swiss, and with no cost for swiss citezens.