Incandescent has done the hard work, but this could all be academic unless your hire company transfers liability to you.
IMO, your primary task is to get them onside* otherwise you'll get a bill for £130/£190 or more**.
*- discussing on the phone is less than concrete. You should write. (
by all means phone and confirm in writing, but I recommend you don't just phone).
**- the NTO would not offer the discount, so if they paid it the charge would be 130. Similarly, you have not said whether the £60 is applied whether they pay or seek to transfer liability, and as it's a charge for a service it's probably subject to VAT, so your total could be ££202.
As regards the contravention, you should look at this, the council's CPZ map.
https://democracy.brent.gov.uk/documents/s45982/10%20-%20parking_management_review_appendix_b.pdfIMO, your approach should be that you were travelling northwards along Walm Road and apparently entered zone MA north of its junction with Melrose when you entered Chichele Road prior to turning right into Anson. A copy of the council's CPZ map is enclosed showing that zone MA commences at this point.
On the day of the contravention (and now..because you'll take photos) there wasn't a CPZ sign alerting motorists to this significant change in controls. And the change is significant because the restricted hours of zone MA are different to those in zone MW(the zone you left and the last CPZ sign which you saw) being Mon-Sat 10-9pm and 8am-6.30pm respectively for this MA zone - the authority will be aware that there are 2 different restrictions in zone MA, the other being 10am-3pm Mon-Fri.
..as a basis...
But IMO get the hire company onside first.
