Found the following info from this link jenstar - looks quite interesting:
http://www.freepint.com/bar/read.php?i=12764
:"The phrase 'Only fools and horses work' has confused many people. Some thought it was a Shakespeare quotation, others that it was the title of Lester Piggott's autobiography. In fact it is an American saying from vaudeville theatre days".
"Of Del Boy's favourite terms, 'lovely jubbly' comes from an ice-lolly called Jubbly, popular in the 1950s, which was advertised with the slogan 'Lovely Jubbly'. Cushty, which means great, is a saying from colonial days when a posting to Custibar in India was thought to be easy".