An "appeal" is what you present at London Tribunals. What you present to TfL are "representations" (against the PCN). if you submit representations to TfL within the discount period, and they refuse, then as far as I know, they re-offer the discount. On the other hand, all appeals at London Tribunals, and, indeed, at all the other UK adjudicators are with the full PCN penalty in play, with no discount option.