I have built a workshop and need to get power to it so wondered if someone in the know could comment on my plans. Having replaced an electric shower I now have a 'spare' 63A 30mA RCD in the cupboard under the stairs. I was thinking of running 6mm SWA from that, through the wall and along one of the roof supports of the 'lean to' into a three way consumer populated with a 40A 30mA RCD and a 6A and 2 x 32A MCBs. One of the MCBs being for a 16A socket to run my Portamig 235 from. The cable run would be about twenty feet so I shouldn't need an earthing rod. How does that sound to those with the knowledge? Do the numbers look ok? TIA.