Formal accreditation to the British Standard can only be proven with an accredited assessed outcome and examination through GT. Not working to the British Standard is entirely voluntary. You can work however you like, but just do not claim to be competent to a British Standard as historically companies have before 31/03/2023 if you are not accredited. Would any competent trades person really ignore a British Standard is the question? If you come to GT prove you are the best whilst working to the British Standard and we will applaud your accreditation and proof of excellence.