Thanks for that - all makes sense.
I think even if I can get away with the current setup it would be by the skin on my teeth ... so most probably not wise.
I've attached a pic of the cable from house to consumer - although is this just the conduit, so hard to tell ... ?
Actually there is a 13A fused switch on the inside of the kitchen (where the garage feed leaves the house) - this isolates the garage.
Unsure how to find out where the feed comes from. I initially thought main house CU, but there is nothing marked for 'Garage'
I have a dethatched garage which currently has a small 2-way CU - 100amp Main Switch, B6 for lights and B16 for sockets.
(Pic attached).
We are doing a basic conversion on the garage into office space. Meaning I'll add probably 1 additional 2-gang socket.
We will be running some office...