Hi, welcome to the forum. In my humble opinion 40MPG is not far off what to expect from the 1.4 petrol version. I hope the following is not teaching you to suck eggs, but just trying to help your MPG:
Always driving with a boot full of junk. @ 2 MPG hit.
Roof rack left on. @ 4 MPG hit.
Driving with all windows open. @ 4 MPG hit.
Driving with A/C on. @ 5 MPG hit. (but switch on weekly to lubricate)
Driving with under-inflated tyres. @ 5 MPG hit. (If you are currently running recommended pressures, consider inflating tyres higher e.g. 40psi. AT YOUR OWN RISK. My Dunlop Sports state a maximum of 55 psi.)
However the biggest variables to interfere with MPG gains are driving style and driving environment:
Best-gentle acceleration, anticipation of braking and coasting to stop in gear, warm & dry air, no stops or congestion
Worst-rally driving style, cold and wet in urban stop & start traffic