Seems like the gardener guy has comitted theft, he agreed to do some work
and was paid in advance, yet work was never done. See the police, or am I
missing somehting here ?

Scraggles

You are very close. It is actually "obtaining property by deception",
contrary to Section 15 Theft Act 1968. This is very much a police matter
rather than trading standards.

Regards

Howard Neil