Your representations text should not mention the worn markings, and concentrate solely on the circumstances of stopping (for pedestrians), because they will reject no matter what you say. This is to force you to pay-up at the discounted rate, rather than wait for the next enforcement document when the discount option is lost. The council know that by refusing all representations, most people, like over 95%, just cough up the discount. It's a nice little earner for them.
The plain fact is the contravention is not made out. The stopping must be due to stationary vehicles blocking your exit from the box, nothing else. If they refuse you and you take them to London Tribunals, you would have a strong case for costs when you win.