My advice would be not to bother. Unless you are 100% confident in what you are doing, taking on debt to invest is unnescarily risk.
On any loan, you will have interest to pay, let's say of 5%. That means just to break even (not make a return) your investment will have to return 5%.
If the stock market negatively fluctuates for a year (possible given recession out of COVID) you wouldn't make money in the market and would be losing money via interest payments on the loan.
Some people can use leverage effectively to invest but this is a risky strategy and reserved for people highly confident in their investing strategy (and even then it can still go wrong)
If that's you - fair enough. For most people, it's probably a poor way to go.
Better - identify a few things in your life you can cut expenses on (drinking, takeaways, subscriptions common) and invest a couple of hundred quid a month consistently over time