Depends where the garage is in relation to the house and if it is detached.
I'm not an electrician, so I'm likely wrong, but instead of ripping up the tarmac can't the connection be done overhead?
Previous rental had the power it's it's external garage done that way. Then again the person who previously owned it was clearly a bit mad and we found a ton of his diy "improvements".
You don't need to ust SWA or MICC. If its going over head normal t&e will be fine. The t&e will be cable tied to a steel catenary wire. The only thing you could say is UV protection thats all. If that is all you are worried about put it in some copex.
Even if you run it underground you still don't need swa or the like as long as it's mechanically protected.
Any work done by yourself will need checking for part p
Sorry Jez Part P will apply to his installation. There are two ways to comply with part P of the building regulations. One is to get a competent person who is registered with the relevant body. Second is to carry out the works yourself and submit notice to your local building authority.
Running twin and earth over a catenary wire doesn’t comply with BS7671.Twin and earth is not suitable for use in direct sunlight as it's not UV stabilized. SWA is a much better choice and make sure the catenary wire is earthed up.
Part P facts:
http://electrical.theiet.org/building-regulations/part-p/faqs.cfm