Stage Tech and Bernard are completely right.

Doubt PLI would cover you for what a court would consider negligence..or lack of 'due care and diligence'. It is also highly unlikely that a court would accept ' a competent person' if he/she did not have the correct qualifications or be a member of a recognised body.

It is a lucrative industry for the guys doing hundreds of them in a day but a small price for an individual to pay to cover his butt!