If you have Barclays then pay £5 for Blue Benefits, then open a Rainy Day Account for 5.07% interest. If you have 2 Direct Debits set up then you get the £5 back, another £3 if you have a Barclays mortgage.
I basically now get £3 for free by having this because i have a mortgage with them anyway.
Next best I think currently is Santander at 2.7%. Chase is 2.05% i think....all are instant access.
Apart from Barclays, the rest should really be higher than like 2% now. Rainy Day account's 5% only applies to £5k, the amounts over that gets pittance.