Currency exchange at Travelex?

Hi I have a Q about money exchange before travelling.
I am going to Switzerland after I went to Germany first I checked exchange rate with Travelex(T) / Post office(P) / M&S(M) T or P seem to offer the best rate.
Now here is the question 1: In DE, Can I buy Swiss fran at T in DE with my UK credit card or debit card(GBP).?
The reason is that I don’t want to carry Swiss fran during the trip in France, I only need CHF the day before I go to CH. 2: T’s exchange rate is from the website. If I buy CHF from T at the airport (let’s say Berlin airport), the exchange rate is not the same as we can buy from the website?
someone said that Ex rate is normally bad at the airport. Please advise. Thanks