Cowboy builder/gardener

I have recently been ripped off by someone knocking on my door offering to cut my hedge.  I know that it was stupid but I had just had an operation and was on very strong painkillers so I agreed for him to re-do my decking and gave him money for the timber as I couldn't drive and he disappeared.  His name is Robert (Melville?) and he is Black British with a London accent.  He is slight in build.  Please be warned by this sad  story of stupidity.