I don't know if I am allowed to use this as I have seen absolutely no documentation, but I think I have found a little gem...
http://www.google.com/ig/calculator?hl=all&q=100GBP=?EUR
returns
{lhs: "100 British pounds",rhs: "124.243824 Euros",error: "",icc: true}
Now does anybody know if there is any restrictions on using this within a web app on my website? There is absolutely no documentation for this, I just found it whilst being nosy when looking for the data source for Google's currency converter.
Many thanks in advance.