For least exposure you need a bank/building society account or premium bonds. For best return in these categories have a look on here: http://www.moneysavingexpert.com/banking/
You can get 5% on accounts fixed for 5 years , for example.
It depends on how much access you need to your money. It also dpends whether you area tax payer. Look to use up all your annual ISA tax free allowance-you can save �3600 pa tax free