Do you need that radiator on? That might sound silly but we have our living room radiator turned off and have a Dragon oil filled heater instead
And the fire. And put the heater where we want it in the room. It is actually not that far from the hamster cage, but it's on a thermostat, so it only comes on when the temperature gets below a certain level and is much more adjustable than the standard radiator. Personally I'd go with the far end of the living room but ensure the radiator is set on low. And have another heat source elsewhere.
As Cypher said, pairs need a careful set up. Which cage do you have.
No levels. Two of everything (houses, wheels, water bottles), scatter feeding is better than using bowls but if you use bowls you want two of those as well. They may only use one but need another one to retreat to if they need space from each other.
Even tunnels etc need to be big enough that they can both fit inside or one can guard the entrance. All the above is to prevent one becoming territorial about the cage or an area of the cage - as that can lead to them falling out.
Even to the point of only taking them both out at the same time. If you take one out for playtime and leave the other one in the cage, the one in the cage can quickly become territorial and not accept the second one returning.
Houses need more than one entrance - two or multiple entrances. So if one blocks an entrance or exit, the other one can still get out. Easiest option is a shoe box or tissue box with holes cut in
If you haven't got all this for tomorrow - the two wheels etc (houses you can make easily enough). Then don't worry - you can add the odd thing afterwards. The main thing is no levels. So no shelves or platforms.
Any change of environment can cause them to start squabbling - eg the move to your house. So once they are in their cage you need to carefully follow settling in needs and keep an eye on things. Settling in needs are basically - leave them alone for a couple of days, then for the next two weeks don't clean out or change things/move things around. This allows them to scent mark and become familiar with the cage set up and develop habits. Spot cleaning mostly is better ongoing anyway so you won't need to do a full clean out too often. Providing you have enough depth of substrate (at least 4" but 6" is better). They may use a sand bath for a toilet but will still pee in various places. The pee is the only thing that needs spot cleaning really and if you can't find it, don't worry about it!
But yes you will need a spare cage in case they start fighting. Squabbles can quickly lead to a fight to the death. If you haven't got a spare cage, then a plastic storage box would do as an emergency cage (at least 60 x 40cm size).