The medium and large pets at home cages aren't big enough either. It is a pain waiting for a cage from Zooplus. The dwarf hamster cage you linked would be a good pet carrier or hospital tank but isn't big enough to keep any species of hamster in permanently. I think you have a few options:
1) Buy a medium sized cage as a starter home (eg 70 to 80cm cage). You would need to keep the hamster in it for a few weeks before upgrading to something bigger. Some people do start them in a smaller cage and then upgrade them. But then you'd have a big Barney cage sitting around. Changing cages is stressful for hamsters so you couldn't just swap the hammy over after a short space of time, or suddenly. Personally I think it's best to put them in a cage and not move them. So one of the other options might be better.
2) Buy a different cage from Amazon (next day delivery) and return the Barney when it comes. If you contact Zooplus they usually ask you to refuse delivery which means it gets sent back without you paying anything to return it.
3) Buy a different cage from Pets at home (you won't get anything bigger than a Hamster Heaven, but it's a good cage). Some branches of Pets at Home stock the Hamster Heaven and the Savic Ruffy mentioned earlier. All the other cages are smaller.
4) Buy a detolf and return the Barney! If you have an Ikea nearby. It costs £40. It's a glass cabinet you tip on it's side to make a long tank. It needs a lid (or two small lids) making out of wood and mesh - but that can be done quickly if necessary.
Here are some examples of detolf Hamster set ups. A lot of people get the Kallax units to stand them on (it needs something to stand on) which also gives storage underneath and looks nice. If you have the space it's a great option. You need a long wall. The advantages are 1) You will not want to upgrade! 2) Any hamster would be happy in one - it's a great cage option. 3) You can have areas of deep bedding for digging.
https://www.google.co.uk/search?q=ha...w=1366&bih=608
The is the detolf itself
DETOLF Glass-door cabinet Black-brown 43x163 cm - IKEA
Here are some options from Amazon with next day delivery (Option 2)
1) The Savic Hamster Sky - similar to the Hamster Heaven but less useless plastic stuff lol. It's recommended to remove the external tubes and block them off (hammies block them up and can get stuck and they are an escape route). Apart from that it's a really good cage with a big front opening door that makes taming easy. You can set it up how you want - you don't need to use the plastic shelves and tubes. Wheel height is limited. An 11" wheel fits fine but a 12" takes up too much space. The Trixie 28cm wheel would fit fine. The 27cm wodent wheel fits well as you can hang it from the top.
https://www.amazon.co.uk/Savic-Hamst...Hamster+Heaven
It's not as big as the Barney but it's a good cage (and Savic cages are good quality in my opinion)
You wouldn't want anything smaller than that for a Syrian. A wheel would take up about a quarter of the floorspace ish.
2) Maxi Duna Multy. This is a 100cm tank style cage, so about the same size floor space as the Barney, but less height. A 12" wheel fits though (not the Silent Runner though). But there are other good wheels. It's a lovely cage if you like tank style cages - a bit expensive.
https://www.amazon.co.uk/d/Cages-Pen...axi+Duna+Multy
Here are some examples of set ups in it
https://www.google.co.uk/search?q=ma...w=1366&bih=608
This is Barley's review of it
Ferplast Maxi Duna