Sorry for the lack of response.
There is a way to import the bank account for different currencies. I will be using USD as an example.
So long at the invoice has been created with the USD currency rate used, you will be able to allocate a bank import and then connect it to the invoice.
Conduct a normal bank import for the USD amounts as per your USD bank statement.
When you import that statement, you will be given the option to allocate the dollar amount to the GBP invoice/bill. The issue with this is that you will need to enter the rate in manually for the day it refers to. This is because the transaction on the bank will be set to the market rate. Any remaining amount will be then FX'd as a forex movement.
At the moment, leaving the FX rate as blank will result in an error and Clear Books will not be using the daily rate from XE.com.