The Colossus debate is interesting.
I don't think there were any
hard plans for Colossus to be at Chessington. But I'm under the impression that there were conversations about a multi-looper (potentially a record breaking one) to be installed at Chessington. How developed these conversations were I don't know and is anyone's guess.
Looking back, as others have said, Chessington was being heavily invested in by Tussauds in the 90s and had a slow build of thrilling rides with the likes of Rodeo, Rattlesnake and Rameses (all of which were popular at the time, remember). It was a very different park to the one it was now. After the successes of Nemesis and Oblivion, and their creativity with getting round planning restrictions, you can certainly see why their would have been temptation for a big thrill ride.
In saying that, the claim that the Thorpe Park fire was the catalyst for the changing markets and Thorpe getting Colossus... No. Tussauds recognised Thorpe's potential to be a more thrilling park way before 2000. There were submitted, hard, plans for a launch coaster on the site of Colossus, which was due to open in 2001. The park changed their minds and went with Colossus in the end, ultimately submitting plans for that in mid-2000.
tl;dr - There may have been some conversations about a ride like Colossus going to Chessington, but it's almost definitely not the case that Colossus as is was planned and then just transferred to Thorpe.
We could be looking at the loss of Rocky, Slammer, CCR and Flume to be replaced by just one ride. I don't like those numbers and hope this turns out to be a more fully formed development with support rides and a meaningful themed area.
I see what you're saying, but that's a bit of a bending of the truth really.
CCR hasn't existed for 10 years now. It closed and Swarm opened. 1 in, 1 out.
Loggers closed in 2015, Derren opened in 2016. 1 in, 1 out.
Slammer died a slow and painful death in 2017. 1 out.
If Rocky goes (and the others) to be replaced by 1 new ride, then yeah, that's 3 out for 1 in. Not great on paper, but given how quiet the area usually is, I can understand part of the logic (not that I agree with the ever removal of small rides mind).
As I say, I see what you're saying and the park should really look to be meaningfully expanding their line up. And I do hope that whatever this investment is, it's more developed than just a coaster - we need a full area with a coaster, support ride(s), shop, restaurant, space for a Fright Nights attraction, etc. But I think to say we're losing those 4 rides for this investment is a little off the mark perhaps/