Unwanted change to exchange rate table

SUGGESTED

When I make a transfer from a GBP account to a foreign currency account, I need to use the actual bank exchange rate.  However, when I override the exchange rate for that transaction, it overwrites the value in the exchange rate table.

This is not what I want.  And I am certain that Sage used to give me the option of overwriting or not.

For my day-to-day transactions I always use the official HMRC exchange rates and do not want these figures overwritten in such transactions.

Is there a way to switch this option back on.  If not, I wonder why Sage chose to this remove previous functionality.

Now I am forced to reset my exchange rate table after each foreign currency bank transfer.  

Regards

Steve