bit of a random question, but i have just bought 20 car clamps and locks from auction for £130 all are working

if i wanted 2 start a clamping company in my local town(swansea) what will i need,
I know i need an sia clamping licence that costs about 1k
any thing else? Permission from the coucnil?
or can i just start clamping illegally parked cars once i get the sia licence?
Thanks for any info