I have now looked at the steps taken on the PCN.

I am now inclined to think that given that the Notice of Rejection was not received that the safest course is to await the Order for Recovery, when the balance increases to £250, and then file a statutory declaration that the Notice of Rejection was not received which will then open the door to the tribunal without running the risk that it will be rejected as out of time as would be the case with any Appeal made now.
We haven't seen what exactly TfL wrote so if they redated the rejection this could be sub-optimal advice so all letters from TfL should be added to this thread so that we can see exactly what they said (if they have redated the rejection we may not be out of time). I like to use imgbb.com , set to do not auto-delete, and then copy and paste the full BB code so we don't have to look at links, we get the full document on screen.