Heidi's apartment is absolutely gorgeous. Spotlessly clean, with everything you need to hand. Super comfy bed, great shower. At a very central location from which you can easily travel all over Oslo by tram, bus and ferry. It felt like we were staying in a four star hotel suite (but without the 24 hour room service!). Which, by the way, you don't need as there are so many places to eat and drink. Don't be afraid to venture further out for some slightly cheaper food options (Oslo is expensive).
Heidi was excellent with her quick responses and great directions and tips and advice.