This is the Ferplast Kios that Racing Hamster mentioned. I also considered it and it's not a bad cage. You would fit up to an 8" wheel in ok, but personally I think a little bit more floorspace is better. The difference between 70cm and 80cm doesn't sound much but it does make a difference to how much enrichment you can fit in the cage.
https://www.amazon.co.uk/Ferplast-Ki...last+kios+cage
For wheels. There aren't really any good 6.5" wheels. The 6.5" silent spinner used to be the popular one but there have been issues with it being stiff and not spinning as well since a manufacturing change. You would definitely need to "try before you buy" with that one. There are a few 8" wheel options which are fine for a robo (mine has a 9" wheel). Zooplus has two -the Karlie wood one and the Trixie 20cm one. The Karlie wood one is silent but would need painting with plastikote to waterproof it. An 8" wodent wheel is fine too (although may need something to hold the base down so it doesn't move about).
https://www.petplanet.co.uk/product_...427&pg_id=2767
This is the trixie wood wheel - it's a bit cheaper on Zooplus but you'd have postage on top
https://www.amazon.co.uk/Trixie-Wood...xie+wood+wheel
Standard trixie wheel
https://www.amazon.co.uk/Trixie-Exer...xie+wheel+20cm
Plastikote for wood wheel - non toxic and water based- a couple of coats helps waterproof (or pee proof) wood items like wheels or shelves.
https://www.amazon.co.uk/Plastikote-...stikote+enamel
Some people make shelves out of Ikea knuff magazine racks too - although the little hole in the end needs blocking off or hammies can get stuck in it.
https://www.google.co.uk/search?q=kn...w=1252&bih=553
It is addictive isn't it! Our last Syrian was my stepson's but I absolutely fell for him and he became my baby
I was heartbroken when he died and we now have another Syrian and a Robo.