You just asked about this a few days ago.
https://www.englishforum.ch/travel-d...-heathrow.html
You need a negative antigen test (not PCR) with certificate to fly to the UK, in addition to the Day 2 and Day 8 PCR tests you have to take on arrival in UK. Many pharmacies will provide an antigen test + certificate for free if you are insured in CH. Some charge a small fee for the certificate. TopPharm Apoteke (at least in Basel) are completely free for the antigen test with certificate. You can‘t get a free PCR test in CH for travel.