Do you have any particular areas of expertise or interest? You could approach sites and publications directly with an expression of interest. Some openly invite expressions of interest – try doing this search in Google to find UK-based writing opportunities:
"write for us" site:co.uk
Or do a similar search for your niche:
"write for us" travel
"write for us" parenting
"write for us" fashion
"write for us" technology
etc.
Pay obviously varies by site. Try to get a link to your writer’s portfolio if you have one (and get one if you haven’t – it’ll be easier to secure jobs). And some will want a mugshot for your by-line.
You could also approach web, copy writing and multi-disciplinary marketing agencies. Good content can make or break a website, so good writers are highly valued by agencies worth their salt.
Otherwise, sign up with as many freelance sites as you can and see which work for you. As well as People Per Hour, UpWork and Freelancer.com are worth a look. You’ll be competing with others bidding on the same work. Pricing low is one way to stand out but that’s a race to the bottom – have some exemplary samples available and work your arse off to get the first few jobs (and reviews).
Don’t rule out
Fiverr. It might seem like a cheapo bargain-basement job site, but most skilled workers command much better rates (perhaps $30-40 per hour). Consider doing some low cost work to get your rating up, then push the higher priced work. The lower cost work might be writing short emails or headlines or something like that – you don’t necessarily need to work long for your fiver
SliceThePie might be worth doing when you don’t have active jobs. You review music, product listings and logos, typically for a few pennies at a time. They’re quick jobs though, and presented to you on a metaphorical plate – no work involved in getting the jobs. If you can write quickly then you might get around £6 per hour.