Tymill, shots look good to me, we always think to chuckout a high percentage, sometimes totaly missing the car when panning
, front could be a bit blury due to upwards movement - not helpful when panning.
Big G, 'Taken with my Canon 450D, f5.6 1/320 shutter 55mm', have you thought about moving the iso setting up, this will increase shutter speed, we mostly up to 400 or 800 outside, other week inside at PDA we were up to 1600 !
(these canons can be used at 400 or 800iso without much loss)