Ford KA difficulty changing from 3rd to 4th gear

poss gear linkage catching on somthing,gearlinkage out of adjustment,fault in gearbox. get garage to check the 3 things above if still the same get in touch with ford customer care for a replacement car. mention car unfit for purpose (if bought brand new)if no luck get in touch with trading standards and state your case

If all other gears o.k , it could be third/ fourth synchro hub .As this fault has been there since you got the car and not improved , get it back to them .Ask them why if "it should clear in a while " it is only affecting that gear .Plus they have acknowledged there is a fault by that statement and you are not prepared to drive it any longer in that condition .Don't be fobbed off and tell them if not getting faults fixed you will contact Ford direct .This should help if you have to ,

http://www.ford.co.uk/Footer/ContactUs

Hope this helps .

sounds to me like they are not interested in helping you out with your needs most dealers are like this only interested in the money and not the after care persue your case im sure something will work out for you