Ukcps

Coupon-mad

Makes no odds really because the exchange of letters won't cancel the PCN. You will end up ignoring them anyway and only treat seriously a court claim (fairly rare and certainly defendable). If UKCPS want to attempt to hold you liable, they have to send you a Notice in accordance with para 13 and para 14 of Schedule 4:

http://www.legislation.gov.uk/ukpga/2012/9/schedule/4/enacted

And they had 21 days to serve that. They failed. You might want to ask the lease firm if they've heard anything and reiterate that this is your dispute now they've named you as hirer/lessee, so if they do get any threatograms, to simply pass them to you please as you are disputing the matter but have not received anything from the parking firm. Remind them there is now no lawful reason for them to be involved or be bothered by UKCPS and certainly not to pay, which you DO NOT authorise. This is now your matter, not theirs.