Simon's Apartment is where Simon lived towards the end of Series 2 and for the duration of Series 3. When Simon discovered that he was Superhoodie, Alisha revealed the apartment to him, and they both moved in together. Before this, it was used as a base/hideout for Superhoodie.
Superhoodie's Tenancy Edit
Using the Time Travel power, Simon travelled back in time to protect and watch over the Misfits. Superhoodie, as he came to be known, took residence in the building. From the look of the building it seems that it was not intended for residential purposes but instead seems to be built for storage purposes or possibly a warehouse, however Superhoodie furnished it for living conditions it is not known if he bought it or just took over an unused storage building. It was later revealed that he had found the apartment because he had it in the future, and it was in need of major work when he first found it. The apartment is accessed by a lift in the centre of the room and has a ceiling fitted entirely of lights most likely inspired from Bruce Wayne's tempory base in The Dark Knight as it is known that Simon is a fan of superhero films and comics.
The apartment was not only Superhoodie's residence it was also his base of operations. The walls were full of photographs of key points in the Misfits' lives and also contained several clocks that counted down to major events in the misfits' lives where they were in mortal danger and needed to be rescued.
After Alisha found out Superhoodie's identity and began a relationship with future Simon she often frequented the Apartment and continued to visit after Superhoodie's death.
Simon's Tenancy Edit
After Superhoodie's death the majority of photos and all of the clocks were removed or destroyed most likely by Alisha, possibly with the help of Simon. Simon later moves in after learning the truth behind Superhoodie, and lives there with Alisha. The rest of the gang often hang out in the apartment but remain unware of who previously lived there and how Simon acquired it. Simon has kept the apartment very similar to how Superhoodie had it, minus the photos and clocks. The bed remains in the same place and the light fittings remain, though Simon appears to have added more furniture. There is also a cupboard with a hidden compartment at the back operated by a button where Simon hides his Superhoodie costume, unbeknownst to Alisha.
During the third series, Simon and Alisha live together in the apartment, and Curtis, Kelly and Rudy sometimes hang out there, unaware of its history as Superhoodie's flat or Superhoodie's true identity as a future version of Simon. Following Alisha's death at the end of the third series, Simon traveled back in time and entered the flat which was abandoned and bare and presumably adapted it to how it first appears at the start of the second season.
Following the apartment's last appearance in Episode 8 (Series 3), it has presumably been left abandoned and empty.