There's a strict process and deadlines for dealing with Penalty Charge Notices.
You're asking for help appealing a Notice to Owner that was sent over two months ago, which is a bit worrying.
There's a 28 day limit for paying or challenging a Notice to Owner. If you miss that, they close the appeals process and increase the penalty to £120. When they do this, they send another letter called a Charge Certificate.
You might want to check your mail carefully because London councils don't mess around and the chances that they haven't sent a charge certificate a month after they're entitled to are vanishingly slim.
Are you sure the Notice to Owner is the latest thing you've received from the council?