Limbo

the pathway to Limbo appears to in fact be above the planets, as a Heaven-like realm

Limbo, also known as the limbo dimensions, was a realm outside the time vortex which physically looked like a White Void. The Trickster was generally limited to limbo, only able to manifest itself in the normal universe fleetingly. His Graske also had access to Limbo, and could materialize and dematerialize in and out at will.

The Trickster had sent Sarah Jane Smith to Limbo when she was removed from time. Maria Jackson was also sent here. (SJA: Whatever Happened to Sarah Jane?)

Limbo is seen as being a complex of clouds

The Trickster put Sarah Jane and the Doctor, Luke, Rani, Clyde and K9 in limbo. He put Sarah Jane in a different looped time than the others. (SJA: The Wedding of Sarah Jane Smithlimbo is most likely the void between dimensions)