Do you have a room thermometer OP? What temp is the room right now? Sometimes it feels colder than it actually is. Also what you have on your feet can make a big difference, Ugg type boots will help insulate your feet from a cold floor and I agree, fleecy lined leggings and/or thermals and jogging bottoms are better.
We use these as hot water bottles, 6 or so mins in the microwave depending on wattage and they stay warm for hours. They are not flexible, but if you can comfortably place it near you, say in a lap-blanket, it would help.
As for your DP not countenancing having the heating on, it's not his decision to make. There are all sorts of single room heaters, but it doesn't do a house good to remain very cold all the time, it's false economy, a lower temp everywhere topped up by a single room heater where you are is much better for the property than to have no background heat as any warm air condenses on the walls because they are so cold.
I think there are Health and Safety regulations about temperature and working conditions for office staff, maybe have a look at those.
You are working to add to the family's income, you can't be expected to do that in conditions that are too cold. Get him to try being in a cold room for the working day, he may change his perspective.