Update: I've been told this is also a possible fix for users experiencing upload issues with Three Mobile Broadband.
This has been covered before here: Hacking T-Mobile Web Proxy, indeed I discovered the fix from that page so all credit to lewiz.org.
However, this is such a fundamental issue as far as I'm concerned that I think it needs more publicity. T-mobile are selling mobile broadband packages and as far as I'm concerned that means the ability to view a webpage how it was intended to be viewed. Not as though viewed on a blurry 256 bit screen.
The problem is more threatening on the Mac because there is no apparent way around it at all. In IE on Windows if you hover over an image you see a tooltip explaining how to increase the quality of the image.
The solution is to use Firefox with an extension installed called 'Modify Headers'. You'll need to configure the extension once after its installed. Click Tools and then Modify Headers from the main Firefox menu bar. Then, you'll see at the top of it's window a drop down where you can choose 'Add', 'Modify' or 'Filter'. We want to choose 'Add'. Then in the next text input enter 'Pragma' (without quote marks) and then in the second text input add 'no-cache' (again without quote marks). Click the add button to add this rule. Then you need to add another rule. Again choose 'Add' from the drop down, then enter 'Cache-Control' and 'no-cache' into the two text inputs. Add this rule and make sure they are both enabled, they should have a green dot by them. Thats it. You should be able to surf away as you expect now.
Of course its still regrettable that one can't use Safari. If anyone knows a way to make Safari modify headers please let us know.