The below is taken from the the HSE guidance and may help you with how to keep your portable appliances safe at work in terms of checks and inspections. Essentially it is down to you to use this guidance and assess the frequency of checks and inspections required. PA testing is not specifically a legal requirement but certainly makes sense to protect people and premises from faulty equipment and fire that is part of existing legislation.
The HSE full guide is here:
Maintaining portable electrical equipment (hse.gov.uk)
