As others have said, wrong Reg.Mark on PCN is normally fatal to enforcement of PCN.
Our usual advice is to make a copy of the PCN, then send the copy to the council with an accompanying anonymous note along the lines of
To whom it may concern
On returning to my vehicle recently I found a PCN (copy enclosed) affixed. As it does not relate to my vehicle I thought you should know.Keep the original very safe: it is your 'Get out of jail free' card should some green muppet at the Council decide to play Sherlock Holmes.
(I can't recall an example of a Council doing this in the past, either here or at Pepipoo.)
The Council cannot re-issue.
Or you could just ignore it - the Reg.Mark on the PCN does not appear to be in use - but still hang on to the PCN.
EDIT:
Ealing council does not seem to have an email dealing with PCNs.
I could send it to general parking enquiries.
It's only through a challenge. The form is asking me if I am registered keeper of the vehicle which I don't think I am as it's asking about the wrong one.
The postal address is on the back of the PCN. Post 1st or 2nd class at any post office counter and get proof of posting. Do not use the form.