Just to let you know how I got with DWP re SMI today. I asked to speak to someone who dealt with this, but the lady took my details as I described in the above posts and went to get advice.
When she came back she said if it was a lower interest rate and my payments would be lower then they would reduce what they contribute . I questioned this saying I thought it was a blanket payment of 3.12% and that when my mortgage int rate increased above this they didn't pay any more and I had to find a big shortfall. Also that I wasn't increasing the mtg in any way. She went away again, came back and said they would reduce the % they pay and could only calculate it when they had all the details.
I decided to go ahead anyway, because either way I would be better off. Next thing I get a phone msg saying that the info given previously was incorrect and that in fact they would still pay the standard SMI rate, but still to get the new mtg info sent through to them.
Isn't that awful! I could have decided against going ahead with a lower int rate deal due to that initial advice!