I was thinking 60A at the main CU and 6mm SWA - I doubt I'd ever run enough power through it to need that, but I'd rather have it and not need it... inside I was thinking 6A for the lights and maybe 40A for the sockets
I'm already commited to getting a sparky now - but what's with the cryptic reply?
If that's wrong - just out of curiosity, I'd like to know what a pro would do differently?
The 6mm cable over an eight metre run will only carry about 47 amps, so 60A at main CU is not suitable.
The normal installation would be 32A at CU on a 4mm cable to a small garage CU with 30maRCD, 20amp power circuit and 6amp lighting circuit, but it really will depend on what load you require both now and at a later date, if you intend to use your garage as a workshop and have equipment that have a high inrush current or higher load demands, a little more thought needs go into your design.
If you installed a 6mm SWA cable a 45A MCB would be more suitable, allowing up to 45A load at the garage.
But also other things on your current installation, as previously stated need to taken in to consideration.
At the end of the day, it's about getting the job done right you need an electrician on board, if it's about having ago yourself you need building controls on board.
The later will cost more money and consume more of your time.