So i have a santander 123 account for the cashback and interest. Whats to stop me having multiple accounts that only require £1000 a month and just cycling that between them? What is meant by 'switching' your account, does it have to be everything or can it just be a monthly transfer?
If you mean multiple accounts with different banks to cycle money through them, then nothing is stopping you. I do it, as do plenty of other people.
If you mean multiple Santander accounts, then that doesn't work as well as you are limited to the number of 123 accounts you can have and internal money transfers (from the same bank) don't count as a separate transfer - whereas the same £1000 is counted when it comes from a different bank.
I have 9 bank accounts that I do this with, but you have missed the boat a little bit, as the banks have tightened up on it all. They have reduced the interest rates/incentives on the accounts and most of them now require at least two active Direct Debits as well, and there's only so many D/D's you have to spread around!
The way to get around that was to use a Tesco saving account that allowed you to set up D/D's to transfer in £1 - that then triggered the reward in the other account, but Tesco just stopped that service in April.
The best ones now to start with is Tesco and TSB, both pay interest on their current accounts and you don't need any D/D's - and with Tesco you don't even need to cycle any money through it - and you can open multiple tesco current accounts.
And with "switching" an account, then yes, you have to fully switch everything and close down the old account to get the switching bonus on the new one.