Anyone arriving in Switzerland from the United Kingdom since the 14 December, regardless of nationality, is required to self-isolate for 10 days from the date of arrival. British citizens currently in quarantine who intend to travel to the airport will need to follow protective measures to remain in quarantine; your local cantonal authorities will be able to advise on this, which may include avoiding public transport.
So where have these tourists been staying if they should have been self-isolating from the time of their arrival?
Why were they allowed in anyway?
On 20 December, Switzerland announced a general entry ban for all travellers from the UK, and suspended all flights between the UK and Switzerland
On 23 December, the Swiss Government introduced an exemption to allow passenger flights to/from the UK from 24 December for the purpose of enabling residents of UK and Switzerland to return in both directions.
Surely the Swiss would want them returned to the UK asap.