Three modest notes about premium bonds. Firstly, you can cash in bonds at any time, so it's effectively an instant access account. Secondly, the current rate is 3.30%. Thirdly, the payouts are tax-free.

3.30% on an instant access account is actually pretty great (best i see elsewhere is 2.51%; i see a six month fixed term deposit at 3.28%), and getting it tax-free without having to have it in an ISA makes it even better.