Total field is not passed correctly to query string

Hi, I have a form with a total field which I want to pass via a query string.
My query string in the form settings confirmation tab looks like this:
name={name1:2}&total={total:54}&method={payment_method:58}

However, the total field doesn't seem to be encoded properly for the URL, in which the query string appears as:
?name=Chris+Booth&total=&#163 20.00&method=Paypal

It looks like the problem is with the '&#163' for the pound sign - the ampersand is being treated as the start of a new variable in the query string, so if I dump the $_POST array, $_POST['total'] is an empty string. Variables following that in the query string (&method in this case) are missing completely.

Form is at http://www.mndscotland.org.uk/fun-run-2012-entry-form/