Add 12V step-down to existing outside light spur

[dannydc]

Hi All

I'm helping set up a shop which is the downstairs of a terraced house (residential flat above), and the sparky installed an LED floodlight over the back door with an almost useless PIR. That spur already has an outdoor junction box by the floodlight. There's a need for some lighting in the old outside loo out back which is around 5m from the back door. What I'd like to do is to:

1. Take the cable from the floodlight and run it back inside into a light switch with an LED (so it's obvious if the light out back is on or off when locking up), then take the switched cable back to the floodlight junction box. Something like this: http://www.screwfix.com/p/lap-1-gang-45a-dp-cooker-switch-with-neon-white/49779
2. Bypass the PIR (or swap for a brighter LED floodlight without a PIR) as it'll be on a switch.
3. Add an IP-rated 12V step-down in parallel with the floodlight, and then take a 1.5mm twin cable over to the old loo and install some 12V LEDs (e.g. http://www.amazon.co.uk/Generic-5050-60D-IP44-Strip-Waterproof-Flexible/dp/B00QX6HKGC/).http://www.scldirect.co.uk/24-watt-12-volt-ip65-constant-voltage-led-driver.html
   Step down: www.scldirect.co.uk/24-watt-12-volt-ip65-constant-voltage-led-driver.html

I mentioned the residential flat above because I believe that means that part P applies, so I can do that work. Can anyone confirm whether the above is ok in principle, and whether I can do it, or whether it has to be a sparky?

cheers
Danny

 

[ban-all-sheds]

I mentioned the residential flat above because I believe that means that part P applies, so I can do that work.

I don't understand that at all. What is is about the fact that the law would require you to make reasonable provision in the design and installation of electrical installations in order to protect persons operating, maintaining or altering the installations from fire or injury that leads you to "so I can do it"?

Can anyone confirm whether the above is ok in principle, and whether I can do it, or whether it has to be a sparky?

It's a shop - there will be various insurance liabilities, H&S responsibilities, possible lease Ts'n'Cs and so on. It should be done by an electrician.