Good luck for the 27th, I'm sure your IVA will be approved and you can enjoy a belated Xmas.
The letters and phone calls don't stop immediately but don't let that worry you, once you have your IVA they can't do a thing to you, some of these companies have so many different departments it takes ages for them all to get the message, just tell them your IVA has been approved, give the contact details for your IP then hang up.
Once again good luck, you have done all you can so try and relax, I hope your approved IVA is your best Xmas present.
IVA COMPLETED ON THE 17th MARCH, FINAL I&E COMPLETED 26th APRIL, COMPLETION CERTIFICATE ARRIVED 2nd AUGUST