You would have to speak to your IP about the change in circumstances. If you could not manage the full payments, it may be possible to have them lowered, but this is something to be discussed with your IP.
If you can't afford the payments, do you have any assets that may be lost if you went bankrupt? You could also consider doing a debt management plan.
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. http://kallis3.blogs.iva.co.uk
as Jan says, you will need to speak to your IP, if you are due to get a lump sum payment from your pension depending on the amount, you may be able to offer a full and final. This is what I am hoping to do