Running power to Garage - Part P obligations

I'm in the process of running power outdoors to the garage. The plan is to dig the trench, lay conduit (this now done), pull through 6mm SWA 3 core cable and then get a professional in to finish the job.

Can anyone advise on the following?

1)
Cable run is only 20m and I plan on only having a couple of lights, sockets for items like a lawnmower or computer so I've been told 6mm is enough:

http://www.screwfix.com/prods/80868...n-LV-Armoured-3-Core-Black-6mm-25m-Cable-Reel

2)
I assume this is just a single cable, I don't need to lay a cable there and back to make a "ring"

3)
I believe the work is notifiable under Part P. Does this mean if I get the electrician in he can finish the installation, sign it all off, give me a certificate and job done. Or, do I need to go further and contact the Building Regs guy at the council myself? If I do, is he going to want to check the trench depth etc etc? I ask because this is all part of a patio project and I don't want to be laying a patio to find I need to let him "inspect" things.

4)
Finally, I'm also thinking about laying some CAT5e cable to join the garage to the house computer network. Would I need to put that in a separate conduit? For conduit I'm just using cheap black waste pipe for 1.40 pound per 2m from B&Q!

Cheers
John

You have a choice - either to do the job yourself in which case you need to notify LABC before you start and pay their fee, they are then responsible for overseeing compliance with the building regs

or

Employ the services of an electrician registered with a competent person scheme from the start - you can't really expect them to sign off your own work.

Spark123 is, of course, correct. However, if you get in touch with a friendly spark before burying the conduit, they may very likely be happy to inspect your work so far on the basis that they will be awarded the job of completing the connections and wiring in the house and garage. Given the limited amount of work you propose doing yourself, I don't think it should be too hard to find an electrician who'll work with you.

The armoured cable does not necessarily need to go in conduit. It is designed to be buried.

The cat 5 will need protection (conduit).
It should be at least a couple of inches away from mains-carrying cable.

For the SWA your trench will need to be a minimum of 450mm deep if under lawn/flower beds etc. , ensure there is no rocks/stones in the bottom of the trench, bit of sand lay cable, cover with more sand or fine earth with no stones/lay cable marker over duct/cables 150mm below the surface.