RE: Derren Brown’s Ghost Train.
As I understand it, the contract with Derren was up. There's obviously been tons of rumours of that Derren wasn't happy with the end result, though the level of truth there is unknown. I do think it's telling that he very rarely advertised it beyond the initial build up and opening, though.
As for it being removed from the app. That's not something which just happens; there almost definitely was intent to do that. It's still listed on the main website, for now, though. So who knows.
Now here's the thing with the attraction. It's very easy to remove all references to Derren. Re-do the pre show, remove Derren's voice from the VR, and a different video in the finale. Rename it "The Ghost Train" (or create a character for the pre show and call it "Professor MadMan's Ghost Train"), and Bob's your uncle.
The bigger issue with the attraction is the state of it. The VR headsets were in awful condition towards the end of last season. The VR itself is many years old. The physical ride stuff is not reliable, and requires a lot of manhours to open and operate. A simple Derren scrub won't change that.
If they wanted to, they could change the experience and turn it into a more Dungeons-esque experience. At it's best, the operations were inspired by Dungeons' operations. Have actor-led storylines on the trains. Create a strong narrative. There's possibilities to have screens in place of the "windows" on the trains (indeed, I believe that was the original before VR came into the conversation). So they could go with that too. Again, if they wanted.
To do it right, it would cost a pretty penny. And it still doesn't solve the issue that the ride hardware is unreliable, a general pain and - bluntly put - overly complicated for something that isn't very good. But it's an option.
Of course, they could just leave it SBNO. The space could be used at Fright Nights. They could in a couple of years use the space for an entirely different dark ride, since the park need one. It's simply a case of how much money Thorpe can spend on it, and when, especially since they've got an expensive coaster coming next year.
One final thing: I see £30m regularly touted as the investment cost for Ghost Train. I'm under the impression that the total investment (ie for everything, including the new stuff in 2017) was closer to £20m; I've heard anywhere between £17-23m. Obviously still a huge sum which could have gotten a big coaster or similar, but not as extreme as seems to be considered.