For comparison I recently sold my 1.6 petrol Renault (non turbo), I averaged 18mph (lifetime as recorded by the GPS), so you know that the traffic was always decently heavy. I also averaged 32-35MPG.
Now here's the kicker, that was loaded with a trailer for a total weight of around 2.3-2.4 tons
If you're interested in improving your MPG, have a read of this:
http://ecomodder.com/forum/EM-hypermiling-driving-tips-ecodriving.php
Some of them are really simple things like planning your trips to mostly make left turns.
Your bulb issue could be the hatch wiring, or just a fault globe. Today's 'smart' cars will actually shut off your lights if it judges the globe to be out of spec.