There's really no room back there that I can see. From the passenger side, there's the muffler, then the spare tire, then a black box...and the points at where you could access the body as a mounting point is fairly thin sheet metal. The Micra is definitely a purpose-built machine. I'm an electrician by trade, which requires me to fabricate solutions, and in this case, I honestly think the hatch mounted bike carrier would be money well spent.
Looking at existing Micra trailer hitches, they all seem to have arms that extend past the rear wheel stabilizer and mount to the unibody frame under the passenger compartment. Perhaps retrofitting an existing Micra trailer hitch from a previous generation Micra would be the way to go if you're insistent on having a trailer hitch.
In our culture obsessed with absurd excess, the Nissan Micra is my counterculture car of choice.
Be sure to visit my blog at mymicra.com
View my fuel log 2015 Micra SV manual: 6.4 L/100 km ... 44.3 mpg (Imp) ... 15.7 km/L ... 36.9 mpg (US) ...