Here's the GBP/CHF exchange rate since 1985, taken from fxtop.com.
The annual exchange rate loss from a Brit's perspective is ~2.7% over those 35 years, far less than the pre-tax 0.9% yield you'd get. Swiss wealth tax is comparatively negligible, too.

While all bets are off due to Brexit, recent years clearly say it'll be bad for the exchange rate going forward. As the saying goes "who doesn't learn from the past is bound to repeat it".