Avoid at all costs!
Any businesses looking to use them, avoid at all costs. Most of the positive reviews here are from people who have bought from other business not the businesses using Trusted Shops.
Will get you to sign up with them. Even hand you a contract and invoice stating the "benefits" you'll receive from them. Then once you sign up, you'll get passed from person to person with each one getting less helpful and only then to find out that they flat out refuse to provide their only USP due to their audit. An audit that was never mentioned until after contract had been signed and by the third person I'd spoken to in the company.