This one is quite good for a hamster (way too small for a guinea pig) - it slots together like a jigsaw, has a lift off roof and a flat roof which can make another platform possibly to put a food bowl on. The door is quite large so it works well with a bendy stick bridge over the door to make it darker inside.
https://www.amazon.co.uk/Ferplast-Gu...inea+pig+house
Rodipet also make excellent hamster houses - but the postage adds to the cost - it's about £8 but delivery is quite quick usually. It's a flat rate of £8 ish whether you buy one item or a lots of things in a bigger parcel.
The two or three room one on here is good
https://www.rodipet.de/shop/haeuser/rodipet-granit/
Be cautious with all the cute things for hamsters
Unfortunately most things sold for "hamsters" are far too small for Syrians and only suitable for dwarf hamsters. Syrians do better with rat sized toys and tunnels. The rat sputnik is popular - works well hung next to a shelf.
https://www.amazon.co.uk/Nobby-Sputn...ds=rat+sputnik
You can choose your own top and bottom colours at Rat Rations
Sputnik - XL - £4.99 : ratRations.com
Rodipet also sell good cork tunnels that are a good length for hamsters (reptile shops sell them but the can be way too big to fit in a cage. Makes a good floor tunnel, something to climb over and adds interesting texture for them.
I have this one. It can also be a bit of a ramp up to a shelf if partly under a shelf.
https://www.rodipet.de/shop/zubehoer...-ca-20-cm.html
Chews are important for them to help keep teeth trim as well. Sugar free ones are best and Rosewood naturals do some good ones.
https://www.amazon.co.uk/d/Grocery/R...ion+chew+stick
I also like their "Little Hearts" treats. We used these for taming treats
https://www.amazon.co.uk/Rosewood-Na...+little+hearts
This was also very popular with our hammy when he was younger. He spent ages gnawing at it.
https://www.amazon.co.uk/d/Grocery/R...HXA0V7BJB04ECG
If you do get any hammy toys, just check that entrance holes are big enough so they can't get stuck (minimum 6cm diameter really). And hanging toys with chains are a bit risky too (they can get a foot caught and end up hanging by a broken leg). Which is why I like the Sputniks - they're safer