Where shall I put my money?

[Mummatotwoxo]

I have 1 bank account, and an ISA that I manage with my online banking. I put money over into my isa when I'm confident I don't need it and won't bring it back over. So my savings have built up to 4K but in the year it's been there I've earned only £1.22 interest on it!!!
Where can I put this money and earn more interest on it, but still get to it instantly if I needed to??

The benefit of a cash ISA isn't that it accrues interest but that the savings are tax free. If you were to invest your cash in something (eg shares, property, precious metals, bitcoin) you might get a return on your investment... or you might not. A starting point might be to speak to your bank or a financial advisor about different types of investment products. A good rule of thumb, though, is don't gamble what you can't afford to lose!

I'm not looking to do anything with my money other than save it

Instant access savings seems to be 1.5% highest interest, so in real terms it loses money due to inflation.

It is your emergency fund, you want it safe, not put at risk, so you will get very little interest on it.

Good rule of thumb for size of emergency fund (when you have no debts other than mortgage) is 3 to 6 months of expenses.

Using interest paying bank current accounts can get you around 5% interest but you need to be moving money between accounts to meet the payment in condition and meeting other conditions they may have such as some direct debits setup.
Have a look at what Nationwide, TSB and others are othering and see if they would be any good for your emergency fund.
Everyone now has a savings tax allowance, so no need to worry about taxes on £4k of savings.

ISA is a tax wrapper, it stops there being tax on growth of the money so is best for very long term things like stocks&shares in my view.