Thanks for posting the picture again
Yes it is small - see my other post above
They need a lot of room to exercise and climb and run about in - especially at night. The Alaska cage might be a good option
And it's not too expensive. Or the Barney cage.
Alaska Hamster Cage | Free P&P on orders £29+ at zooplus!
Both the Alaska and Barney have good deep bases as well as giving them lots of deep substrate is good so they can did and burrow a bit and make mountains out of the substrate and other hamstery things
It doesn't have to work out more expensive in substrate either because if it's deep the bottom half tends to stay dry, meaning less cage cleans and you can manage with just spot cleaning (ie taking a handful or two out and replacing it) most of the time. Plus you can get substrate in bulk a lot cheaper.