Here is a suggested text, feel free to modifiy :-
Dear Sirs
Re PCN <number> issued on <dd/mm/yy> at Shardcroft Road
I deny responsibility for payment of the above PCN on the basis that the contravention did not occur.
On the day in question, I parked in the bay located by No 8A. I saw the suspension notice and read where it applied. There are three separate bays on the even-numbered side of Shardcroft Road, one by No 8a, then one by Nos 8-12, then a further bay before the junction with Kestrel Avenue.
The suspension notice read, and I quote, "All parking bays, all car parking spaces, from outside 8 to junction with Kestrel Avenue on Shardcroft Road". Therefore this defines the suspended bays as the one outside 8-12, and the next bay before the junction with Kestrel Avenue.
In view of this clear definition of the suspended area, which does not include the bay by 8A, I therefore request that the PCN be cancelled forthwith.
Yours faithfully