Not sure I totally understand this, so I will just toss out the numbers
from my statement, all transactions seem to have "about" the same
percent charge, this transaction occured on Aug 15, 2006 on a Chase
VISA card.

GBP 1271.18 x 1.89553071 + 72.28, charge on statement is US $ 2481.92

My calc shows the effective rate as 1.9524536258

*note when I worked out the first line by hand I got a difference of
72.36 instead of 72.28 as shown on the statement.

Bank of America ATM access through Barclays was GBP 250 for $477 which
is only 1.908, a MUCH better exchange rate.

Unfortunately both the credit cards we used were from Chase, so I don't
know how it compares. Anybody else have some recent transactions from
other credit card providers.