Oh, and it's meant to look rusty, it's themed around an abandoned mine!
But it's the only ride in the park themed like that now. It just seems out of place.
Scorpian Express is an old train running through a desert, so it does still tie-in with RattleSnake and the Mexicana area fine. I don't know where people are getting the idea of Mexicana being "cut in half" from, all the buildings are being repainted and Scorpion Express will still be in this area.
I'm getting the "cut in half" idea from this part of the Chessington website:
Scorpion Express is a brand new ride experience for 2014 set within Mexicana’s Scorpion Valley
They have made a sub-group within Mexicana, half of the rides in it, half not, essentially cutting the land in half.
Also, I agree that Scorpion Express has some throwbacks to the original deserted mine theme, but I believe there's a lot more to it this time, with the animatronics and fire. As opposed to being in the deserted mine, it's more:
Adventurers must board the old train of the Scorpion Express as it’s the only way to cross the sands, ruins of the mines, and abandoned town.
It is no longer just rocky mines in my opinion, but a lot more, and Rattlesnake hasn't been getting this, which makes it seem different and outdated in comparison.