Do they also offer one of the most competitive rates for exchanging currency?
The same exchange rates are used for any currency transaction, when the cheque is recieved and processed, it would be the same as if you had withdrawn the currency. However, there is a charge for conversion depending on how the cheque needs to be processed, and ranges from around 6.50 to 12. Its usually 6.50, and the branch wont be able to tell you which processing method is used as that is determined at head office.