The Swiss authorities don't recognise the concept and if you are the beneficial owner of the account then you should declare it on your tax returns so if you are being straight there's little advantage.
Wouldn't it be easier to maintain a UK account for the GBP element?
I want to be able to access a UK mortgage without paying the buy to let premium and I know UK offshore accounts let you do that.
Going offshore is the same, except way way more expensive.
Tax isn't straightforward (when is it?) as I'm coming on an expat deal and am tax neutralised. The main issue is convenience and access to sterling financing without paying a buy to let premium on my mortgage.
Open a safe deposit account and put Swiss Francs cash in it.
With interest rates at 0.125%; banks charging fees; tax deducted at 35%, you are not going to make anything on interest.
Off course if you were not to declare the cash in your safe deposit box on your Swiss Tax Return you would save Capital Wealth Tax I have been told.
Most mortgage companies wised up to this market a while back - i.e. at least 5 years ago - when they automatically started charging more for buy-to-let mortgages. You could buy a house, but if you put tennants in it without declaring it then you could get into trouble with the lender if they find out.
That's my understanding of it anyway.
Oh, and another thing, off-shore accounts are not protected (or minimally protected) by the government in case of bank devaluations - as happened only last year.
All-in-all just keep your on-shore account for managing your mortgage and declare everything (unforunately).
I would also say (although, re-reading your post, I'm not sure this is relevant to you):
As stated above, you will be taxed on all global assets by the CH authorities, so there is no real "off-shore" element to your CH tax position as far as I can tell - unless, as economisto said, you are not going to declare your money.
As an expat, you would also be exempt from tax deductions (assuming you are going to have an agency managing the property for you) from your rental revenue in the UK, so again, no benefit to an off-shore account.
Credit Suisse definitely do a GBP current account. I have one as part of my Bonviva Platinum account. You can also have them for USD, EUR, JPY. Youdon'tt get any interest on them though.
Transfers out and in have been free as far as I can tell, but interest is minimal.