I've seen a really nice daypack (+-30 litres) made by Dakine that has a padded laptop sleeve. I'm using a Crumpler zip-up neoprene protector for my 14" laptop, which allows me to stuff the machine into any old pack without too much worry.

OP, if you're still in NZ, The Warehouse advertised them, laptop backpacks. They didnt have any at our local so cant say what they're like.

It would have been nice if the OP came back and clarified whether he is looking for an actual backpack or a daypack.
I'll even guess that the laptop backpack you are talking about westwood is in fact a daypack. I've never seen or heard of an actual backpack with a laptop compartment.

Just because you havent heard of one doesnt mean they dont exist!!!!!!! Unfortunately the flyer it was advertised in has been recycled otherwise I'd give more details.

OK westwood, I'll concede that a backpack might indeed exist with a compartment for a laptop. That wasn't my point. The point is we don't know whether the OP is actually looking for a backpack vs. a daypack. There's a big difference, no pun intended.
Daypacks are small, backpacks are big. Daypacks are designed to carry enough for the day, backpacks are designed to carry enough to live life out of.
Daypacks designed to take a laptop are common. I have yet to see a backpack designed to take one. Simple statement.

I am actually looking for something in between a daypack and a backpack. When I travel, I travel light, but a daypack is just a tad small....
Up until now, I've simply used a sports-type bag and housed my laptop in a padded sleeve. The problem is that its a pain trying to get anything out of my bag as the laptop takes up all the space right at the top. Hence, my search for the ultimate laptop-friendly pack...I might hav eto design my own. Who knows, it might be a good business.

None of them looks big enough to carry much of anything radson. They are all daypack size.
Vidaboa, why not simply buy a small backpack and use a laptop sleeve? Or, I might even suggest a travelpack with a removable daypack. Find the right one and where the daypack zips off, you can slip the laptop between the daypack and the backpack if you get my meaning. Or use the daypack for your laptop.
Here is an example. http://www.eaglecreek.com/bags_luggage/adventure_travel_packs/Voyage-65L-10051/