I understand that DebtMatters have recently sold the majority of their IVA clientbase to two other major firms (I will not mention them on the forum in case my intelligence is incorrect), so you may find an improvement in service in due course.
In my honest opinion, there is no point in this meeting proceeding, and your IP (whoever that may now be) ought to advise creditors that it is not proceeding given that you have caught up with your payments - albeit you are one month behind. Neither you, nor your creditors, should be charged for the meeting - if you had paid over the money before the report was issued. If the report was issued before the money was received, then that is simply a timing issue, which your IP can appraise creditors of on the day of the meeting.
None of this is likely to jeopardise the IVA - creditors still would rather be paid at the end of the day.
Regards, Melanie Giles, Insolvency Practitioner