Is this your only savings?
What rate taxpayer are you?
Have you used your ISA allowance this year?
Do you have a partner you are willing to split the money with to maximise tax and interest allowances?
What scenario do you have in mind for needing to access it? A small amount to replace white goods, a medium amount to replace a car, or all of it to use as a house deposit or similar?
For the best return, the answer would vary slightly depending on the answers to the above questions.
Eg, if you don't expect to need all of it, but might want to access some of it, you have a trustworthy spouse and neither of you have used your ISA allowances this year, the best return would probably be if you both put £20k in a one year fixed rate ISA and then you put the other £10k in the best instant access account you can find, which should pay around 5%.
But if you answer no to any of the above questions, then you can't do this.