If you are in receipt of overseas income or capital gains, no matter how little it is, you meet the criteria for completing a Self Assessment Tax Return. ax in the UK is calculated by default, using the 'arising basis' on all of your world-wide income and gains would be taxable in the UK. As you are resident in the UK, but not domiciled, you can opt to choose the 'remittance basis' of tax, which means that you only pay tax on your UK income and gains and any overseas income and gains remitted to the UK. As you have paid tax in the UK on the income you sent to your savings account in India, you would only need to declare the interest arising from the capital in your savings account.
Have a look at section 9 of RDR1 as the remittance basis is not always the best option.
Guidance note for residence, domicile and the remittance basis: RDR1
Overseas income and gains should be conferted to pounds sterling and declred on the tax return. The rules for taxing savings interest would apply equally to IK interest as it would to overseas interest.