Savings are not taxable. It is the interest that savings generate that is treated as income and is taxable.
You will need to review the guidance at RDR1 below, to determine your residence status for the tax year in which you arrived in the UK.
Residence, domicile and the remittance basis: RDR1
Where split year treatment applies, you do not need to declare any income arising outside the UK, prior to the date you arrived in the UK.
If you are resident in the UK, but not domiciled in the UK and you do not bring your savings interest to the UK, then it is not taxable in the UK.
If you are resident in the UK and domiciled in the UK or deemed domiciled in the UK, then your foreign savings interest is taxable in the UK.