I think you are looking at this a bit back-to-front. Level 3 is by no means the highest grade of electrical qualification and any person installing, maintaining, repairing, replacing any electrical accessories, working un-supervised, in a work place that unskilled members of the pubic can have access to, must be fully competent as to establish that any remedial work is still electrically safe complying with all relevant regulations in BS7671 and will not pose any danger to people, property or livestock. If you are working under the supervision of someone else, who is suitably qualified and competent, then basically you don't need much experience or qualifications.
But if you are working alone, other than the basic industry recognised qualifications, I cannot see how anyone could prove in a court of law that you were competent to be opening up any electrical accessory and verifying that your own work is safe for others to use. DIY in your own home is a different matter, but if you make a mistake in a public building you could seriously injure or even kill someone very quickly.
Doc H.