One way to watch the Sidemen Story is to look for it on the official YouTube channels of the Sidemen. They might have uploaded it there for their fans. Also, check if it's available for purchase or rental on digital stores like iTunes or Google Play.
I don't know who Toby is specifically in this story without reading it. He could be a child, a little animal, or even an adult with a child - like sense of wonder during Christmas.
Since the title only gives us the name Toby in relation to a Christmas story, he could be a variety of things. He could be a kind - hearted person who spreads Christmas cheer around his town. Maybe he's a lonely soul who finds warmth and friendship during Christmas. He could also be a naughty character who has a change of heart during the holidays.
One way to watch The Sidemen Story in the US is to check if it's available on subscription-based channels like Amazon Prime Video or HBO Max. Sometimes, you might also find it on free ad-supported platforms, but the viewing experience might have ads.