they are Thermal vacuum switches, in other words they let the vacuum through or not once at a certain temperature. the one on the thermos housing lets the dizzy signal vacuum through from the carby once the engine is warm (its pretty cool when it opens <50 degrees cel) then it also has a constant manifold vacuum port that opens at about 110 degrees cel or around there when the car is running hot to try and help cool it down by (advancing?) i think the timing a little, it does this by suppling the manifold vacuum through to the dizzy at all times instead of the ported vacuum it normal gets from the carby.(ive had a mental blank on which way you adjust the timing to help cool the engine), the other TVS on a blue motor im pretty sure at the front of the head is just a switch that triggers the exhaust flap, it allows manifold vacuum through until the engine is warm then closes. And the exhaust flap is closed by vacuum so it then opens, allowing the exhaust to flow freely. Its just an emissions thing to help it warm up quicker.
There should also be a TVS around the middle of the head, it actuates the EGR valve, and that TVS opens when the engine is warm to normal operating temperature. It allows ported vacuum from the carby to open the EGR valve allowing lovely exhaust gas back into the engine.
