80c or 80f ?? 80 Farenheit would be about 26.6c which is pretty hot. There are no legal requirements as such in regards to high temperatures. Your employer is obliged though to provide fans, air con, proper ventilation and so on.
A few questions though, the answers might help reduce the heat.
Is the heating still on? Most office buildings will have computerised heating systems that are probably still programmed to have the heating on full blast all day. You could check this and turn off the heating.
Can you open windows to naturally ventilate the building? If there are windows on both sides of the office (open plan), open them both, this allows air flow through.
Does the building/office have air conditioning or air handling units? Check that they are working correctly. Your employer is obliged by law to keep these in running order.