Dodgy parking company using threats to collect on Lidls ticket

At the start of february I received a parking fine for parking over the time in the Greenock branch of Lidl's. I disputed this and on 27 February received a letter to say that they agreed to waive this charge and would notify TPS Parking Solutions of this arrangement. In between this I had sent a cheque for £45 to TPS just in case. However, this was returned to me as, in all innocence, I had forgotten to sign it. At this time I was still waiting for the result from Lidl but had received a letter in response to my letter asking for further details. I sent a copy of this letter to TPS who in return wrote to me saying that "further to your representations, we will hold this charge at the current status for a further 114 days from the date of this letter". The letter is dated 26 Feb. Lidl waived the parking charge in a letter dated 27 February. TPS however sent me a further "Legal Action Pending" letter dated 12 March. In response to this I sent them an e:mail saying that the fine had been waived. They replied that they were still looking for payment. I called Lynn Hynds of Lidl at this who said that she would contact TPS again telling them to forget it. Yesterday (30 April) I received a Bailiff Appointed notice from the National Enforcement Services with an amount due of £142.31 for this fine and saying interest is accumulating and that a bailiff may attend with a warrant and remove goods or vehicle. Can you advise please?