This is very interesting. I am descended from Lings who I know were definately travellers, mainly active in Derbyshire (Alfreton, Ripley) and South Yorkshire (Barnsley, Doncaster). They were mainly general/marine store dealers and china/earthenware dealers, though some of them settled down later. The furthest back I've got to was George Ling, who came from Hundon, Suffolk (b. 1824), though most of his descendants were active in Yorkshire/Derbyshire, so I wonder if the Lings you mention who ran the funfairs are related to him. There's a few stories in our family about distant cousins being involved in travelling funfairs.