Aside from synthy type stuff, if you’ve not visited your friends in Sheffield before, it would also be a good place to explore the UK further (especially The North… which everyone knows is the best bit
).
If you are the outdoors type you are close to the Peak District (on it’s doorstep in fact) and also close to the North Yorkshire Moors and Coast (my favorite part of the country
).
If you are into cities York (really close), Leeds (again really close)+Edinburgh and London are all easily reachable on the train.
Peak District:
North Yorkshire Moors+Coast: