If you have an account with Nationwide, you can go to any branch to ask them to issue you a cheque on that account, as far as I know. Well, I have done that in the past, I can't see why it would have changed. You might need ID.
I live between two towns and use both branches as regularly as each other. I have also used various branches whilst on holiday in the UK and never encountered a transaction that cannot be carried out anywhere.