"Since it is not a TT install, you won't need RCD protection at the head
end of the SWA "

Could you explain the significance of this please ? I've a TT system
with the garage something like 16m away fed off a 15A fuse in the
house (seperate CU from the main split load CU with RCD). In the
garage there is a split load CU wirh RCD and an earth rod effectively
paralleled with the house rod.

Rob