As a single person with one income, I would always prioritise minimising risks rather than maximising returns ( and I've still invested for many years with good returns). This is a different strategy than that which would suit a couple and even many singles.
I would:
Beef up the emergency fund to two years worth of expenses, plus sufficient savings for initial private medical consultations. (A broken leg with complications for instance, and 6 months fund can disappear rapidly).
Buy some critical illness insurance to cover your salary that kicks in after the two years of savings are depleted (the time delay will reduce premiums).
Pay off all debts, including mortgage, regardless of the interest rates (minimises debt risk). Paying off the mortgage is still an investment in property.
Transfer your cash ISA to a better rate (Trading 212 for instance pays 4.9% on its cash ISA).
Investments are attractive because over time it beats the eroding effect of inflation on cash savings and preserves wealth. They are inherently risky and some more volatile than others. When inflation rears its head its not a dragon easily slain - there may well be more to come in the pipeline.
The US stock market has made fantastic gains over several years. There are warnings about it being overvalued and overheated. The 'Magnificent 7' tech stocks are dominating the S&P 500 index, and also the Global market Index. They might continue to do so and grow exponentially, or the bubble might burst.
My exposure is now limited to 30% of my investments in this market. It feels a percentage I am comfortable with. I may lose out on more incredible gains but it fits with my risk averse strategy. I still have a toe in the water there.
At the moment short term money market rates are beating inflation - Vanguard Sterling Short-Term Money Market Fund is returning about 5.13%. These tend to be much less risky than stocks, with a steady return.
I also utilise 5% of capital to invest in undervalued markets that I think might give a good return in growth or dividends. I stick to index funds and low cost platforms with a transparent fee structure.
(I'm not a financial adviser and my strategy might not suit your profile).