Have you followed the proper burping procedure?
The AW11 cooling system takes almost 12L of coolant, so an inch drop could be from it not being filled properly to begin with.
You need to have the heater fully on (so turn on the car and crank the heater all the way up then switch off the car), there's a bleeder valve there (under the bonnet right up the top of the firewall, you may need to remove plastic trim to get to it). Connect the "service hose" i.e. clear plastic hose to it and turn the tap on top until you see coolant run up the hose.
There's also a bleeder valve at the top of the radiator on the passenger side; remove the plastic trim between the headlights and it's right there. Again plastic hose here and snake it around the bonnet prop and turn on the top until coolant runs up the hose. If coolant doesnt run out then either you haven't opened the tap enough, or you are missing a lot of coolant!
In the engine bay you need to find the thermostat housing above the gearbox, there's a plastic screw there that needs to be taken off; this is usually the first point where coolant runs out, so if you remove it and coolant overflows there immediately, just put the screw back in straight away. Also make sure both the rubber O-rings on that screw are in good condition.
With those 3 bleed points checked. undo your coolant cap, and fill coolant until all three bleed points show coolant in the hoses and it overflowed on the thermostat, and no air bubbles escaping, and no coolant level dropping at the cap.
Once you think you have filled it enough, close all the bleed points, and turn on the car without the cap on. make sure the level doesnt drop at the cap, sometimes it can overflow a little bit too, so don't worry if it does, if it over flows a LOT though the warmer the car gets, then you may have a head gasket issue.
Run the car for around 2mins without the cap on (by this I mean have it idle in your driveway, not actually drive it!). switch off the car, fit the cap all the way on then take the car for a drive and see if it overheats then or not.
If you lose coolant at this point, take it to a mechanic who can perform a reliable cooling system pressure test, as well as an exhaust gas detection test in the coolant. This will not cost you a lot of money and will give you a definite answer if there's either a head gasket issue or cooling system issue.