@Les and @Sarah Bee
Rather than ODFOing, I've just thrown together a little greasemonkey script, that will replace any Dollar values it finds in the body of a register page with the appropriate GBP equivalent, it also deducts the 15% VAT from the final GBP figure.
So in my browser, your comment Les now reads:
"Whether the software is "worth £46.38" is not a relevant question to most UK readers, who will have to consider if it's worth £69."
I suppose you could use it on other sites too if you change the settings.