I don't understand why anyone would want to keep 800k tied up in a bank account after year 1. Surely if you were depositing an additional 65k per month from the beginning of your 1st extension based on retirement, you then have 12 month's statement based on regular income so the 800k is no longer needed?
Transferwise charges a percentage of your transfer, meaning larger transfers attract significantly higher fees. CurrencyFair also allows you to transfer an unlimited amount, while TransferWise limits your transfer to $200K.