DocOx:Hi,
So, keeping my situation in mind, what are my options?
You should open the required account with a mainstream bank before you move. You need to ask the question whether it will be ok to keep the account after you've moved overseas. It will not be possible to open a UK account after you move but most (obviously not all) banks and building societies will let you keep any account that has already been opened. It should not be necessary to look at offshore accounts.
You mention UK taxes. I believe that if you are working overseas for a complete tax year you may not need to pay UK income tax, but I think that you'd need to be paying tax in another country for this. This may be something worth investigating.