Citroen will charge about £300.
But if you get the part (ebay, search for picasso regulator), a garage will fit it for about £40.
http://cgi.ebay.co.uk/CITROEN-PICASSO-RH-ELECTRIC-WINDOW-REGULATOR-MECH-ONLY_W0QQitemZ380136823208QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item5881eb99a8&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1683%7C293%3A1%7C294%3A50
Will, July 2009