I first saw this in PC World...
Tucano Microfibre Script Second Skin Macbook 15.4" - Grey
Looked nice, came with the additional keyboard cover, but was £30 and I'd still have to find something to put other bit like the power supply in.
Note: Just found it on Amazon for £23.99...
http://www.amazon.co.uk/Tucano-Micr...1_4?s=computers&ie=UTF8&qid=1346140470&sr=1-4
So I bought this to start with...
Staples 16 Pocket Laptop Sleeve
http://www.staples.co.uk/office-supplies/new-office-supplies/16-pocket-laptop-sleeve?r=bf
Super cheap, just to protect my rMBP while I found something better.
I then spotted this in Comet...
Port Designs Marbella Series 15.6 inch Notebook Briefcase - Dark Grey
Not too big, space for the essentials (power lead, USB Hard Drive, HDMI Cable, TB > VGA Adapter, etc... but it was at some silly price, around £50, so didn't bother.
Quick search online when I got home and found it on Amazon...
http://www.amazon.co.uk/gp/product/B004SO8SE4/ref=oh_details_o03_s00_i00
Works a treat!

However, the pocket for the rMBP within the main compartment is a little spaceous as it's not designed for such a slim unit. But the foam insert that was inside the cheap sleeve I bought fits perfectly to pad it out and provide extra protection
