Finally got them all in the tank, all is well, but it's 11 pm so it seems I may have miscalculated the duration of the acclimation. Top tip guys: if you wanna sleep, don't buy your shrimp at 7 pm!
All the shrimp have settled in fantastically (in the 15 mins they've been in the tank) and I am already so happy to have this. Honestly, when I got into the hobby this is what I was looking for. Not 10 shrimp scattered through a giant 110 Litre aquarium, who I can never see. A small tank with nearly 20 shrimp, so I can see at least 10 at a time, with very small fish who interact with the shrimps, and the shrimp being out and about and happy. It's really fantastic, and I'm remembering again why I got into fish- and shrimp-keeping in the first place. Will assess the shrimp tomorrow, check for any problems, but for now I am stoked with my new shrimp. Here's a couple of photos below, of the shrimp on my hair algae tufts and moss balls. Made me so happy to see them enjoying those.