57 plate avensis 2.2 D-Cat T180 thermostat replacement

[Fatgaz1972]

Hi all, I'm new to the forum and new to being a Toyota owner and so far it's not so good! There is no heating at all coming from the driver side air vents and is very slightly warm coming from passenger side. I have checked and topped up coolant which made no difference. I've checked oil filler cap and dipstick with neither having any kind of white/milky residue so I'm assuming not head/gasket issue. I was informed by a mechanic that it maybe the thermostat needs changing, I have a new thermostat but where is it on the 2.2 T180 D-Cat engine? Some pics would be fantastic! Temperature gauge is showing just slightly below half way which I'm assuming is about right? Any and all help would be greatly appreciated!