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A lot of people figure that it's common sense issues with most portable professional gear.
Sound systems have to be careful with their gear too, most venues say they need PAT stickers but no one ever checks.
I don't want to diminish the importance of the PAT test in scenarios where no one wants to take responsibility for equipment but owner operators who don't care about frayed power cables or faulty extension cables probably don't care about PAT testing either.
TLDR - A lot of it is common sense you will already be applying.
Since Portable Appliance Testing isn't specifically a legal requirement I think you need to ask the people that are asking for the testing what they will accept. There are plenty of places that will do a 1 day course, or even online, for £150-200. A tester is a similar cost.
Course on a USB stick for £90 https://www.pat-testing-course.com/shopping-cart.php?product=PASSUSB, exam another £60 from them.
Random tester https://cpc.farnell.com/seaward/primetest-50/pat-tester-handheld/dp/IN04993
Don't forget some stickers https://cpc.farnell.com/seaward/91b038/pass-labels-1000-pack/dp/IN01675
Edit: It's all risk mitigation and passing the buck really. Would your insurance cover you if you got it wrong and something bad happened?