What should I do with my savings (12k)

Hi,

I currently have my savings in a savings account at 4.5% interest however this drops in July. I’m trying to work out what is the best solution. My expenditure for the month is £1135 (worst case 1500 if I didn’t have my partner) and I am trying to work out how much I should have as an emergency fund and if I should open a stocks and shares ISA. My car is a 2022 plate and trying to keep it as long as possible and I don’t have any other debt (bought a house last year so don’t need to save for a deposit for that). My income is 31.5k a year.

Thank you