costing for garage instalation

[Engineer54]

due to the garage being 30m away, a 30m run of 6mm swa would definitely increase the zs considerably.
and just to be on the safe side i thought an earth rod in the garage would be a better bet.

I can't see that much of a problem, but easily remedied by the use of a 3 core SWA instead of a 2 core...
What would you consider better, ... A TN system of under 0.35 ohms at the origin, or many 10's of ohms that is also possibly unstable?? A no-brainer, if there are no other mitigating circumstances such as water/gas services that needed bonding back to the MET...