Garage conversion (ish)

I have a fairly standard (I think) brick and breeze block garage that is as built by the builders (the house was new 8.5 years ago and I have just bought it from the previous owners). I'd like to tidy up the garage, add stud walls (damp proofing, insulation etc), add a ceiling and semi convert it so that I can use it as a workshop. This will be a bit of a project for me, so I just wanted to know what people think I can do on my own and what I should seek professional assistance in doing? I'm fairly handy and am willing to put the hours in, so is there anything I would need professional support completing? The wiring is something I am particularly concerned about as I think the sockets in the garage are just a spur from the main ground floor ring but they may be a radial circuit. If they are a radial circuit, am I able to convert that into a ring circuit myself without a part P qualification or does that need to be done by a professional? If my suspicions are correct and the sockets in the garage are a spur from the main ring (I will check tonight - been working away from home for quite a while) and I want a new ring installed that needs to be completed by someone with part P right? For the lighting, I can make changes to that myself right? Adding in another switch and adding a few more lights etc? I won't be using low voltage, which I think you need a certification/qualification to install so that should be OK? Many thanks