Help with Jumping Spider (UK based)

[Noctomnis]

Hello! My friend has left me in charge of looking after her jumping spider while she's in America, I think the vivarium is too cold for it and I'm worried it wont survive the UK winter. The thermostat is showing around 16c but I've read that jumping spiders need around 25c so I've adjusted the base temp to 25 but it isn't going up at all. The heat mat was also previously placed on the bottom so I've moved it to be against the wall instead as I've seen a lot of people recommending this. Here's a photo of the setup!


Vivarium Specifications:

1. Mantis Den Medium Enclosure: (Link)
2. Heat Mat 7W (Link)
3. Thermostat (Link)
4. Substrate: Just regular planting soil.

 

[Veno Manus]

Well the mat won't really heat the enclosure it's just going to keep that side warm. If you keep the room warm with a space heater that should be doable for the time being. But I'd keep the the heat mat on just if it drops. It will always keep it warm at least. They call for the 70-80° range since they are from warmer places so try to just keep the room warm at the very least. I've had hundreds of these spiders and all have molted and eaten very well in room temp. I have a lower watage bulb that provides light and a bit of heat in case the situation but it's not overboard.

 

[Ratmosphere]

What's the room temp? If you're around 70 degrees F you will be totally fine!