There is another 100cm cage I've considered before as well - on Amazon.de which ships to the Uk. It's like two barney cages on top of each other (and one version with 3!). One level has a big front door, like the Borneo, the other level has the top door and two smaller side doors, like the Barney. I thought long and hard about this cage before getting the Barney. But the floor area isn't as big (on one level) as the Barney, and although you have two cages effectively, you lose some floor space due to the entrance from below. But the three level one could be amazing! the other reason I didn't go with it was, at the time, we had an older syrian hamster and climbing ramps was becoming an issue.
So I went with maximum space at floor level in one cage (ie the Barney).
This is the 3 tier cage. Not cheap!
https://www.amazon.de/PETGARD-M%C3%A...gateway&sr=8-2
And this is the two tier version
https://www.amazon.de/PETGARD-M%C3%A...gateway&sr=8-1
They do have 7mm bar spacing like the Barney so could be used for a dwarf hamster as well. And no fall risks in the lower level due to the solid "roof".
The cage size/base is fractionally smaller than the Alexander - 98cm by 52cm (Alexander is 101cm x 52.5cm). The Barney is 100 x 54cm