Question about invite to disciplinary meeting

[rekrab80]

I was sent a letter by email inviting me to a disciplinary at work and given just over 48 hours notice, which the company policy says is the minimum. The letter detailed the allegation, possible outcomes and explained my right to be accompanied. Just after the email with the letter was sent, a calendar appointment also arrived in my inbox. My manager then cancelled the meeting without giving a reason, a few hours before it was due. I complained to HR that this was unprofessional. They apologied, still without giving me a reason, and said the meeting would be moved to Monday at 2pm.
So far, my manager has not sent the new calendar appointment - I assume he will do it on Monday morning.

Am I being pedantic to refuse to attend unless they send another letter with the new time and date, and giving me 48 hours notice? So far, the only formal letter I have is the one inviting me to a meeting that got cancelled.

[ULA]

You have already been given a letter to attend a disciplinary meeting with the requisite details and notice as per your company's policy.

Just because it is cancelled and rearranged then no, I would not expect the company to send a completely new letter with a further 48 hours notice..