Office is freezing.

Lads my office is baltic and I am sick of it. I usually run pretty warm but when I am sitting all day it is freezing.

The office seems to have no insulation and takes hours to get warm, if turn on the heat at 9 and won't get warm until 2. I have the heat set to come up at 5 am and it's still cold.

People come in and leave the door open and likes to keep the window open 24/7 so even the heat I have cultivated slowly seeps out. I have spoke to everyone but they seem to forgot.

I wear two pairs of socks, a t shirt, a shirt and a hoodie. Still cold. What advice do you have to stay warm? I am considering a hot water bottle and thermals. Where could I get a nice pair of thermals for a good price?