I need to find out where thethermostat is situated on my bmw 316 i se 1999 e46 shape. The heater is blowing cold air, i think that it may be the thermo - can u help?

i presume you have checked the coolant level? If you temp guage is quite high. but still no internal heating then i would be little worried.

It will normally be just where a coolant pipe enters or exits the engine block, powered by an internal or external drive belt. Sometime this is part of cam belt or alternator belt.

If it is quite old or worn, you may need a new gasket to reseal it proper or just slap some gasket seal on the old one.

To answer your question - the thermostat is located in a housing at the top left-hand side of the radiator.

the thermostat is at the end of the top radiator hose, where it connects to the cylinder head...

and it may not be the thermostat... make sure the water level is upto the mark, or no water flow thru the heater matrix, and no hot air...

Its on the front of your engine follow the top rad hose down to the thermostat housing.
Hope this helps