TUI are twats. They emailed the day after my case was opened by CEDR to say they'd already replied to me!?
I sent a snotty email back saying I had disagreed with their previous correspondence and that they had ignored my request for a written final answer. Arseholes.
I had very similar experiences dealing with the Energy Ombudsman and Avro Energy recently - they denied they had received correspondence from me (fortunately I had an acknowledgment email to send to the Ombudsman to prove they had) and claimed they had written letters and issued refunds to me when I had received nothing.
Everything regarding Ombudsman replies etc was left to the very last date they were allowed to respond on, as was the payment and apology which they had to send to me after the ombudsman's final decision. They also managed to tell lies in their replies to the Ombudsman which of course if you correct this and update the case gives them another delay for a chance to respond to your update!