Idk much about the UK, but here in the US grinding is very popular in clubs. And honestly, it's easy to build sexual tension. You;ve got the hard part down, they;re coming to you! Be confident, keep dancing, smile or wink at one of the girls, and don;t hesistate, as soon as you see any IOI, grab her hand, NEVER FROM BEHIND!. If you want to grind, grab her hand and twirl her, and then you can grind. Don't be creepy.
If your clubs are more relaxed dancing, rather than sexual like clubs here usually, you could always just dance next to her, across from her, and once a song is over, pull her aside and just say "Wow, did you learn those moves from me

?". Sorry if i'm not much help here, as I face more grinding heavy clubs.