Looks like you're stuck with 'just practice', highnotes. I'm still really bad at technical work - 18 years later! I just don't seem to bother memorising scales etc very well. Also, I have crooked middle fingers on both hands, so I have a bit of a reach problem (particularly with dominant and diminished 7th arps in inversions! Ouch!!

), and my technical work can tend to be uneven at top speed!
Don't freak out and do too much practice and hurt yourself. If you're having problems with smoothness, practice *sloooooowly*. If there's also an uneveness, 'swing' the notes (I know that can sometimes be hard for pianists who haven't been exposed to much jazz) deliberately. Another fun thing I get my students to do is overemphasised staccato: take your hands waaaay off the keyboard in 'bouncy' movement which creates a nice firm, crisp staccato still. Play scales at a moderate speed - still slow enough that you can get all the notes right and have complete control of where you go to next. It gives you a lot of control.
I'm sure you'll be fine though - as far as I'm concerned, if music is 'perfect', it can be quite boring, and I often prepare pieces to be 'unperfect'!
Also Kate, I know this is Australia, with a different system and examiners, but we usually get the benefit of 2-3 strikes and then you're out for tech. I even had an examiner for my 7th Grade AMEB sax exam who ticked my sustained altissimo scale when I didn't know how to play the notes: my teacher at the time was a trumpeter, so the guy took pity on me!