Bank statements can be easily changed.
Give me 30 mins with a PDF version or slightly longer with a scanner and I can make it say anything I want.
Unless the OP's bank would send a statement direct to TfW, but they ain't gonna do that, even if the OP insisted.
Ergo, a bank statement doesn't show innocence.
The OP needs to consider why they said a different origin station.
Even in a panicked state (why were they panicked?), I don't see how that would make someone say a different point of origin.
If the OP was panicked because they knew they had a problem, having no ticket, then either explain and pay again, or offer to pay again. There should be no panic about the truth.
Yes, a bank statement can be faked. So can a witness statement by an RPI, or for that matter
any evidence out there. In fact recently even "video evidence" of the US House Speaker Nancy Pelosi allegedly saying something was faked by dubbing it over. Nothing is 100% watertight, and that's why Courts deal in likelihoods of the truth - i.e. civil cases are (mostly) "on the balance of probabilities" (is the claim 51+% likely to be true), whilst criminal cases are "beyond all reasonable doubt" (is the accusation ~90+% likely to be true).
A bank statement is strong, even if not 100%, evidence that a certain amount was paid to a ticket office/TVM. Those places usually do little other than sell tickets, i.e. accept fares, and thus it isn't a massive leap of imagination to say that the OP paid a fare there. The fare to where, you might say? Well, it just so happens the OP was later 'accosted' at Cardiff, at a time that will just so happen to match up with the timings of buying a ticket at Neath, and then taking the train from Neath to Cardiff. And it just so happens that the amount they paid is the amount of the fare to Cardiff.
Yes, none of this is outright
proof that the OP paid their fare to Cardiff, but even in the slightly unusual circumstances of the OP's giving of an incorrect origin station it is
still is a good indication of that they have paid their fare, and certainly by my mind more than sufficient to give reasonable doubt as to whether they are guilty of the S5(3)(a) offence. If the Court found so too, the OP would be acquitted of the offence.
We've been over this several times and I really don't see what discussing it again adds for the OP.