I've been continuing my own research/comparison and i thought i'd share my thoughts.
Pictures and Internal Dimensions:
Kata
28.5cm x 16.5cm x 20.2cm
This certainly looks well padded and an intelligent storage solution. I like the bright interior and it looks like a strong shoulder strap and i like the included rain cover. (Shame its yellow)
Not sure how it'll handle bumps against the odd tree/chair/door/car/passing cyclist though.
Canon
23cm x 16.5cm x 13cm
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This model just looks too small. Maybe i should be looking at another one in the range, but i don't know Canon products well enough to know exactly which one is a match for the other two. One thing i am concious of is "Canon" does scream, There's a camera in this bag. A least a little more than Kata, but maybe the same amount as Crumpler or Lowepro.
Lowepro
28.5cm x 16.5cm x 18.5 cm
I like Lowepro products and their build quality is excellent. I love my Fastpack 350 and this has the feautures i am used to. But the extra pockets and storage on the Kata give it the edge. It is certainly the sharpest/cleanest looking out of the 3. Some of the alternative Shoulder bags look like Army Kit bags with pouches for grenades, groundsheets, ammo and a 3 man tent.
Overall, Its clear the Canon is going to be too small for the job i had in mind. Does anyone else have the Kata bag? Do you have a comparable kit list and what are your thoughts?
Another question

, does anyone know which stores tend to stock the Kata range? I think i need to take my kit along and pack one up with my stuff.