I believe it works out around 20mpg. Nowhere near acceptable. I would have the car serviced and the temp sensor checked. (A failed/failing temp sensor could cause the cold start to be 'on' during the time the engine is hot.) Of course I am assuming you are driving in a reasonable manner, and that you cruise in the highest gear.
I had the same engine in my Escort. It did easily 47 miles to the gallon in the city. One thing I know is that doesn`t matter what the engine size the car has, and talking about if you have a 1.6 and takes aprox 7 liters to 36 miles than its wrong. Bigger CC gives you more torque so dont forget that the horsepower to put it on the wheels needs torque. So what I`am saying is dont buy smaller engine car just make sure that you using it within the right rpm and as previously said take out all the "not important luggage" . Your spending on fuel is allways depends on the weight-bhp (torque) ratio. And the focus (have one) is as heavy as the old vectra (had one) they are like tanks. If you change car than go for an 9 years old corsa 1.4 petrol. Lovely car good MPG. "fun" to drive.