To help you choose a dating site browse UK dating sites via a Google search or similar. Most will let you have a site tour for free and you can see if the design, ethos and format of the site appeals to you.
Some sites are built around hobbies, interests or politics (such as for those into sport or seeking a vegan animal lover) so you may want to pick something where you’ll meet like minded people.
It’s worth signing up to a number of sites and also being very clear in the sites you chose and your profile what you are on the site for (like dating, friendship or just sex).
That way you end up using the right site for the right purpose and don’t end up matched with someone who’s just into friendship when you were hoping for something more.