Backpack for M860TU

As I should be receiving a Kobalt Nexus (clevo M860TU) shortly, I'm on the lookout for a good backpack. Important features would be good weatherproofing and padding, especially the floor of the bag.
However this needs to be able to hold a lot more than just laptop/power adapter/external hard drive etc...
I'd like enough space for a flute (stored vertically I imagine - this is why a well padded floor would be good), large water bottle, Sennheiser HD595 headphones (these are awkward to carry, and I'm not sure what the best solution here is... is a case available for these headphones?), as well as other odd bits and pieces - paper/books (small books), food etc...
Comfort is definitely important, and the ability to have delicate things well secured (not that I'd run flat out whilst carrying, but the ability to jog (crossing roads...) with it on is handy).

Now, I've looked at slappa, and I honestly don't like their backpacks (styling for the velocity matrix/spyder, and lack of versatility for the ballistix aura pro-tour).
Same goes for booq - unless someone can convince me otherwise!
I've been hovering around Tom Bihn's website, and almost plunged for the brain bag with vertical brain cell, but the lack of padding in the main compartments, and altogether spartan design means a few diy jobs would be in order.
My preference is for an understated look - so it wouldn't attract unwanted attention.
I've tried to sift through the numerous targus/swissgear etc.. bags, but there's just so many models on the market that I don't know where to start.

I'm in the UK by the way.

Any help guys/girls?