OP, you posted:
....I was told at the Notice of Rejection on June 6 2023 [the council's timeline says NoR issued 16 June] that ‘If, after 28 days, you take no action, we may send you a Charge Certificate increasing the £70.00 charge by 50%. You will then have 14 days to pay this increased charge. If after 14 days this charge has not been paid, we may apply to the County Court to recover the money, plus court costs, from you.’
Which means you received the NTO, made reps and received a Notice of Rejection.
What box exactly did you tick on the witness statement??
If you received the NoR then you don't have legitimate grounds to challenge the Order for Recovery. Also, if - as they are required to do - the authority refer the matter to the adjudicator you would be asked to substantiate your claim which with the current evidence you could not do.
Setting aside for one moment that another NTO might be hoving into view from Brighton, the matter is procedural:
What box did you tick on the WS;
Did you receive a NoR;
Did you just tick this because there wasn't an option to claim that you didn't receive the Charge Cert?