Hi yade and welcome to the forum.
On the face of it your I&E looks fine, but hopefully one of the experts will be along to assist with that.
I'm with Payplan as well, and apart from a glitch at Christmas, have found them to be excellent. I had a payrise last September and when I rang to tell them, I was informed that they wouldn't look at it until my annual review which is due March/April time. I've just had my quarterly review and my payments haven't gone up.
You do need to speak to someone at Payplan to get this sorted out as you obviously don't want it to fail.
If you have no joy with your case worker, try emailing your IP direct with your concerns. You can contact them via this link:
http://www.insolvency-service.co.uk/newipsearch.htm
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley.
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