I am a member of NAPIT on what they call the just 8 scheme, its made for semi pro's who don't carry out more than 8 notifiables a year hence the name. You still have to jump through all the same hoops as the pro's, ie test equipment, insurance, paperwork, assessor looking at test techniques at one of your jobs. Looks at quality of your work aswell. I would recommend them as it sounds like you are doing the same thing as me and doing the odd job now and then. Cost is £240 pa and insurance through swinton's was £60. All notifiables are costed at labour plus £40 to cover my direct costs. Hope this helps. If you want to talk over the phone, repost back and I will e mail phone number. I can't fault NAPIT.