kapz's dashboard

I have recently moved abroad. All my transactions until that point had been in GBP. I have now changed my base currency to NIS and all new transactions in new accounts/categories appear in NIS.
However, if I post a new NIS transaction with a category that already had a GBP transaction posted, it converts from NIS to GBP in that category (so that my reports are mostly in GBP, etc.). As I now live and function in NIS, I would like all my reports to be in NIS. How do I change my base currency for all the categories to get my new transactions posted in NIS?

Many thanks, David