Hmmm, there's a number of things it could be Steve, the throttle cable is a likely suspect but there are some others too.
We can rule out:
Sticking butterfly (unless you have recently squirted the bearings with WD40, this'll cause your symptoms, but i have no idea why anyone would want to do this...
Warped throttle body (ali don't warp!)
OK, now onto the more likely cuprits:
1 ) Easy one first! Check your driver's mat, has it crept forwards? Look for signs of wear in the region of the pedal (symptoms of a trapped mat)
2 ) Throttle cable - if it is kinked then it could cause similar symptoms, likewise if it is too slack (cable could be jumping out of it's groove on the throttle cam). It is unlikely to need lubricating, but this is a possibility. Check also the parcel shelf carpet isn't causing a kink in the cable (it happens). Lastly check the metal tag is seated properly in the end of the accelerator pedal arm (and the metal retaining clip is in place)
3 ) Throttle position sensor - this is secured with 2 screws on the reverse of the throttle body - if the screws are over tightened they project out the back and can foul the return spring on the throttle body causing similar symptoms.
4 ) Lastly check the plastic bearing on the accelerator pedal pivot - this is secured with a pair of circlips and it can wear (but this is unlikely in a car this young).
Hope this helps mate. Got a spare pedal assembly sitting in my garage if you need me to take any photos.