Incorrectly Wired PIR Security Light

[DG77]

At the rear of my house there is a PIR security light overlooking the garage pedestrian door and oil tank. This light has been daisy-chained with some soffit lights into a 6 gang 2-way light switch at the back door of my house. This 6 gang switch controls all exterior lighting at the sides and rear of the property and rear hallway/porch.

 

This isn't ideal as I can't leave the PIR security light on without having the soffit lights on. I'm trying to figure out the best way to separate these out so that I can control the PIR security light independently.

 

The simplest thing to do which would mean no rewiring is to convert the soffit lights PIR equivalents. However, I'm not keen on that idea as we have enough PIR lights around the house and they are in an area where rabbits and neighbours cat frequents, so there would be numerous false activations. I have a strong preference to have the soffit lights and this PIR security light separately controlled.

 

I thought about separating out the PIR security light and wiring it into a free gang in the 6 gang faceplate. However, the electrician only supplied 2 conduits into the backbox and each already have 3 t+e going down each conduit, so there is insufficient space for another cable.

 

My next thought was to control the PIR by converting the 1 gang garage light switch to a 2 gang switch and diverting the feed from the PIR security light to this switch. This back box is supplied with 3 t+e. First is a cable out to the lights (2 daisy-chained LED batons), second is the power and third is unused in the faceplate and cut inside the garage access with a little excess remaining.

 

In the back box, earths are connected, neutrals are connected and lives are switched. Spare cable is totally unused.

So, what I'm thinking of doing is as said above - change the faceplate to 2 gang and connect the PIR security light into this faceplate. However, what I'd like to do is to pull the PIR security light cable down into the backbox rather than using the existing cable, if at all possible in order to avoid a junction box and the unknown spare t+e.

 

I've no visibility of the conduit entering the garage attic as there is a joist in the way. I think looking at it that it would be a tricky path to pull to get it into the conduit. Is there any way to successfully pull the cable down using the existing spare cable? My method of pulling t+e with another t+e would probably not be streamlined enough to get around joist.

Any suggestions as to how I could pull this?

 

Can I intercept the live feed to the 6 gang switch in attic and join the PIR security light neutral and earth there? The Live to the PIR security light would go to the back box for the 6 gang switch using a single.

It would work, but is it acceptable practice as there would be a junction where the PIR security light meets the soffit lights (to extend the cable over to the switch) and again above the 6 gang switch.

Are singles allowed for this purpose? 

 

Thanks.