You can dispense with 'the driver' if it's you. This is owner liability and if you were the driver then your evidence is first-hand and any reps submitted would carry more conviction.
Noted. I was erring on the side of caution.
As stated, there's no 'grace' period of 10 minutes in Wales and as far as the evidence is concerned and irrespective of when you parked 14.37-15.08 is more than 30 minutes.
I understand that the period parked is more than 30 minutes, but I hoped the PCN could be rendered invalid due to a fatal flaw.
As suggested, asking them to accept that the contravention was de minimis and that they should exercise discretion would seem to be your best bet. Don't risk antagonising them by reference to valve positions unless you know the vehicle was not parked as alleged, in which case it's 'contravention did not occur' but you'd need evidence.
I will submit an informal appeal today asking for the PCN to be dismissed on the principle of de minimis.