Here's a tip for anyone searching for accommodation but getting nowhere.
Sites like Trivago and booking.com are showing inflated prices and no availability left close to the venue. But I decided to email a few of the places directly, and I was able to get a single bed room across the river for £280 Tuesday-Saturday. It is one of those shared bathroom type a deals but I've stayed in lots of them whilst travelling so it's no problem. I actually love places like that since you can meet so many great people. It's a good deal, and I'd say less than a half hours walk to the venue. Here's a picture.
Its also right beside Cologne Central Station so transfers to and from the airport will be hassle free. My flights, and Gamescom tickets are also booked so I can now look forward to a lovely 4 day break next month.