Santander are offering up two ISAs at the moment, the Santander Loyalty Flexible ISA paying 3.3% and the Santander Flexible ISA paying 3.15%, basically to get the loyalty one you have to qualify with terms such as:

You already qualify for this great rate if your current account is with us and you pay in at least £1,000 a month, or you have a Santander mortgage or investment subject to the qualifying criteria below
You switch your current account to Santander using our dedicated switching service and agree to pay £1,000 each month
Our Loyalty Flexible ISA does not allow cash ISA transfers in.


more information about the Santander Loyalty Flexible ISA can be found here:
Loyalty Flexible ISA - Savings: Santander

more information about the Santander Flexible ISA can be found here:
Flexible ISA - Savings: Santander

Why choose a Flexible ISA?
Enjoy the certainty of a guaranteed minimum rate of 3.15% AER tax free (variable) for 12 months
Tracks at 2.65% above the Bank of England base rate for 12 months
Flexibility to access your ISA money online, at a cash machine, in branch or over the phone
You can open your cash ISA with as little as £1 and save up to £5,100 this tax year - from 6 April 2011 the cash ISA allowance will be increasing to £5,340.