491 miles/790 km.
You can't. The London Underground and London Buses only go as far as the suburbs.
It depends from where in the UK to where in Switerland. Assuming you meant London and Zurich, the answer would be that the distance between London (UK) and Zurich (Switerland) is approximately 780 kilometers (~ 480 miles).
The total driving distance from London UK to Zurich Switzerland is 628 mi. A road trip from London UK to Zurich Switzerland would take about 10 hours 17 mins.
The air distance from London, England, to Zurich, Switzerland, is 483 miles. That equals 777 kilometers or 420 nautical miles.
About 1 hour from Zürich HB to Basel SBB. It varies depending on which train you take.