Low Voltage Directive

UK

Guidance Notes on the UK Electrical Equipment (Safety) Regulations 1994: https://webarchive.nationalarchives.gov.uk/ukgwa/20100304130556/http://www.bis.gov.uk/files/file38623.pdf - whilst the legislation has been superseded due to Brexit, the content is still useful and largely applicable

EU

LVD guidance: https://single-market-economy.ec.europa.eu/sectors/electrical-and-electronic-engineering-industries-eei/low-voltage-directive-lvd_en
Harmonised Standards: https://www.legislation.gov.uk/uksi/2016/1101/contents
Legislation: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014L0035