Reclaiming Stamp Duty

jonkyl

I already owned the first and second floors of a detached house.  Last year I bought the ground floor flat and, as it was treated as a second home at the time I had to pay Stamp Duty of £8000.  I was then granted Planning Permission to convert the property into a single dwelling, and this is now complete.  The property has been registered with the Land Registry and Council tax rated by the local Council as a single dwelling.  I also own the Freehold.
As I now do not have a second home, should I be able to claim back all or part of the Stamp Duty?  I contacted the appropriate Authority, but they were less than helpful.  
Any advice would be gratefully received
jonkyl