There's no validity requirement if you have a residence permit, which you do. I travelled recently with less than a month left on my passport and it was fine. I wouldn't recommend renewing your passport at the moment. Mine has been with HMPO in Durham for over 3 weeks and they've still not acknowledged that they've received it!
Same for me. SwissPost said it was delivered to them registered post on the 3rd May. Just checked and still saying send us your old passport. Good thing I don’t need it urgently.
And yes, had no problems entering the UK at the end of March and leaving first week in April with a passport expiring on 6th May. Mind you we drove to the UK and back rather than flying.
Thanks - so my take home is that as long as I bring my C permit with me I will be allowed to fly back in to Switzerland regardless of how little time is left on my passport.
As a Swiss resident, if you present a British passport you might well get an entry stamp anyway. (Except if you enter Schengen via Geneva or Zürich airport).
As Jim2007 suggested earlier have you checked with BA whether your passport is acceptable with your Swiss permit or not? They’re the only ones who can tell you yay or nay.
Isn’t this link posted by Spaceghost earlier in the thread official enough for you?
You will have more than three months validity left on your passport plus a Swiss residence permit when you return so there is no reason for them to deny boarding.
Often the check in staff don't work directly for the airline. In your case you really don't need to worry, even if I only had a day or two left on my passport I still wouldn't worry. There's so many UK Schengen residents travelling back and forward that they all know it's fine as long as you have a valid residence permit with you.
In my case it both flashed up at check in and at the gate "DO NOT ALLOW TO BOARD", first thing airport staff asked was whether or not I had a residence permit. All over within 20 seconds.
“issued less than 10 years before the date you enter the country (check the ‘date of issue’)”
So my passport will have more than 3 months until it expires, but will also be more than 10 years old. So even with a residents permit looks like I can’t come in.
Not all EU countries are applying the issued within 10 years rule. I’ve seen nothing to indicate that Switzerland is. The airline is the arbiter. Check their web-site or IATAs. https://www.iatatravelcentre.com/
IATA produces the TIMatic (electronic Travel Information Manual) the gold standard for unbiased travel information. Most airlines, including non-member LCCs use this as their guide.