It doesn't sound great however I think you need to carry out a more accurate check (fill tank to brim, zero trip meter, run until needs refill, re-brim, check mileage and calulate). It would also help to know more about your city driving, journey length, is it all low speed, low gear, lots of stationarly engine idling stuff? Is the engine getting upto temperature? have you checked tyre pressures, brakes binding, have you had the A2 long? have you driven diesels before? Are you using branded fules? Try running some Redex or Millers additives for a few tanks. Sorry for all the seemingly unhelpful comments however annalysing such a problem is not straight forward. What car did you drive previously and what consumption did you get from that?
If the car is only used for city commuting it may simply need a good long fast cross country/motorway (100+ miles) run to blow away the cobwebs every few weeks.