Ah I think I understand.
Cash ISA doesn't require you to pay tax on anything below £5,640 in a tax year. I'll pop into my branch tomorrow and speak to an adviser.
Any money you remove cannot be put back in though. So on the 1st day of the new tax year you put in £5639, and then withdraw it. You can only redeposit £1 tax free.
Natwest online only accounts offer a semi decent rate of return, you just transfer any money you need online to a holding account when you need to withdraw it.
It's not a savers market though.