Greetings Paul , I notice that you felt you needed to say you were new here and " go easy on me " I guess you've visited a few times and seen a few "unfriendly" threads . That is not what this Forum is about .....please feel welcome ....ask away ... you are going about it in the right way , not blundering on , getting advice .
It can be a bit daunting , but can also be liberating without a boss breathing down your neck . However I'll list a few things I can think of .
Do you have some jobs lined up ?
Do you already have some commercial customers ?
(1) Basic PL insurance is usually £ 2m cover for domestic only or £5m cover for both. Not that expensive , shop around but whatever you do ...do NOT mention soldering or gas torches or welding . Just general contracting including 3 phase.
(2) For domestic work you need to notify most jobs to Building Control under Part P of the Building Regs....they need to know that you are "Competent" . The only sensible way to do that is to register as a Domestic Installer with a trade body . So NICEIC, ELECSA, NAPPIT, and the cheapest STROMA .
Approx £440 or half that with STROMA.
You have the qualifications , you will need test instrument for Continuity / Insulation / Loop impedance / RCD trip times.
(3) Contact HMRC and National Insurance, tell them you are self employed from whatever date . NI is nothing like what you pay as employed but only covers your state pension . (Make sure you keep the payments up)
(4) Start a private pension when you can afford it.
(5) There is no " Right time " other than , have you got some work to start off with .
(6) Keep your accounts simple . An accountant for a sole trader shouldn't be charging more than £200 to do your books as long as you've presented them in a decent order . I can advise you on that . Don't let bookkeeping phase you but whatever you do , keep all wholesaler's invoices ...petrol ...road tax... van insurance...van repairs... tools ... computer ... I'll do a proper list when I get a minute.
(7) VAT registration threshold is £83,000 PA , if you do a lot of domestic , don't go there , you'll never win a quote . Commercially , your customer may want you to register although you are under the threshold . thats a decision you'll have to confront .
(8) If you do a lot of commercial / industrial work do try to open a 60 day account with your wholesaler , not easy these days , usually 30day but most commercial customer terms are 60 day . This means you will be subsidising them for 30 days and that is the Disaster Road at 100 MPH . Most domestic jobs of course , pay on completion.
(9) And FFS make sure you put away YOUR INCOME TAX FOR THE COMING YEAR
Others will be adding their advice , theres a lot of experience on here
And as Steptoe said , most of us , including me , are electricians NOT businessmen. And thats how I like it .