Taking in the various sets and props from the hugely-successful eight-film series, the 'Proud' group also enjoyed experiencing what it is like filming on a broomstick in front of the green screen.
Wearing Hogwarts robes, Aston Merrygold, Marvin Humes, Jonathan 'JB' Gill and Oritsé Williams were snapped on their brooms, with Merrygold making sure to find the most comfortable position.
Fans of the big-screen adaptations of J.K. Rowling's novels will also have the opportunity to fly a broom, while stepping foot on the cobbles of Diagon Alley, getting up close to Ollivanders, Gringotts and Weasley's Wizard Wheezes joke shop.
JLS also stopped to marvel at the intricately-detailed model of Hogwarts School of Witchcraft and Wizardry.
Various stars from the Harry Potter series will attend the grand opening of the attraction on Saturday, March 31.
JLS's official Sports Relief single 'Proud' is available to download now.
> JLS behind the scenes on Team GB London 2012 promo - watch video
Photo gallery: Pictures from The Making of Harry Potter studio tour: