Sounds like something is wrong as we did Swansea to Chester on the weekend with a shit load of stuff in the car and averaged 30 mpg with a turbochanged sport ka (well, normal ka with 1600 sport ka engine and a t2 turbo which comes on boost at the touch of the throttle).

SportKa gear ratio's are really close which won't help, they're slow even with a close ratio box lol

Service it (and do the fuel filter) then go from there, coilpack and lambdas would be next on the shortlist if the service doesn't help much

Sport Ka injectors are 230 cc/min which is the same as a 2 litre zetec so it's probably humping the fuel in!