The inconsistency in the way money is being spent across the UK RTPs (excl. Warwick) at the moment is really interesting. Possibly frustrating.
Chessington has needed heavy investment for years, and I expect Jumanji to be the first of several medium to large investments in the coming few years. It is also good to see Chessington being smartened up - although I would argue that Chessington was probably the second best park for presentations in the four RTP parks. Legoland has always been smart, but like Chessington has suffered from a poor set of rides and low capacities. Again, this has been addressed and I expect, like Chessington, investment to continue at Legoland as, to put it plainly, it's a total cash cow.
Thorpe Park and Alton on the other hand have plenty of larger rides, but presentation is appalling in many places. Grotty, tired looking rides in many areas and cleanliness in many places is disgusting. Investment in these parks seems to be to build a large ride every few years and on the interim period - it's minimal - with poor effort in infrastructure, logistics and other. But when you see Chessington and Legoland getting smartened up - flowers, pathways etc. - to see Alton stuck with Dark Forest and so on... it's quite frustrating. I don't know why Merlin do not seek to improve the presentation of all of their parks.