Whilst we know the relationship between you and your dad, we still need to know why you told your dad to sort it out. Who is the registered keeper? You or your dad?
If it is you, as I suspect, and your dad was the driver, then we do need to see the original Parking Charge Notice (PCN) that was received by you. Also, why was a payment to Gladstones made, irrespective of whether it never went through? Someone has tried to admit liability for the charge and they could use that against you.
Don’t worry about the attempted payment if it was made by your father, not you, and it failed anyway, so no money changed hands. That doesn’t mean you’ve admitted anything. Even if it had gone through, it still wouldn’t be an admission of liability unless you personally had made the payment and said you accepted the charge. Just sit tight and wait for the claim form from the incompetents at Gladstones – they’ve got a habit of filing claims with defective particulars, which we can deal with when it arrives.
Up until the point of a claim being issued, liability for the PCN can still be transferred to the driver, assuming the PCN was fully compliant in the first place (unlikely). However, once a claim has been issued, the person named in the claim has to deal with it, irrespective of their status as the Keeper, the driver or both.