Tilly, you pay in a minimum of £500 a month and pay a fee of £2 per month.
You have to set up a number of direct debits (2 or 3, check this) but you get cash back on payments to your gas and electric suppliers, your mobile phone bill, your broadband/tv/landline bills I get back about £5 a month on these bills.
You get 3% interest on balances up to £20,000 but you must keep at least £1000 in the account.
I didn't close my original current account, I just set up a standing order for £500 a month to the Santander account and shoved £20k across and 3 direct debits. I get around £55 a month back.