Hello, I am Keith, one of the experts on Just Answer, and pleased to be bale to help you with your question.
You can find all details of the agreement between Swiss Banks and the UK Government here:
Whilst exchange of information between tax authorities is an expanding area of activity I can find no information regarding the cessation date of the Double Taxation Treaty between the UK and Switzerland. Your pension will continue to be taxed under Swiss rules and under the Treaty any tax deducted will be allowed as a tax credit against your UK lax liability on the same income stream. Your banking arrangement will remain as they are at present.
From whence did you get the idea that the Treaty is to be terminated? Actually it is being strengthened.