UKCAT scores must be updated every year, if you reapply to a uni, and universities do not look negatively at this. Postponing your UKCAT for a later date is fine too, although I would advise you to inform the UKCAT team and rebook asap.
If you feel like postponing would improve your score and hence your chances, do it. Make sure your future date is available first though.
Best of luck.
If you need any help regarding the UKCAT or want some of the resources I used to prep, just send me a PM.
How would retaking the UKCAT change the way universities look at my scores? I haven't taken the UKCAT yet but I did choose a date thats near by and I'm not sure if I'm ready, would you say postponing it or retaking it is a better option?