The easiest way to make complaints to TSS is to call Consumer Direct on 08454 04 05 06, it's a National number but on a landline you'll get through to your local branch - on a mobile you have to input your postcode.
CD will refer any potential offences through to the relevant TSS.
Their database is National also and can be seen by the OFT and TSS. If enough complaints go in regarding certain 'traders' then they are flagged up.
Calls are 4p per minute from landlines, mobiles vary as always but you can ask them to provide a direct landline number.
You can also send complaints in via webform on their website:
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