I'll check the sockets - I'll leave the CU alone tho
Yes as mentioned in above posts, it is important to safely isolate the installation prior to any work being undertaken.
You must also be aware that when the main isolator at the CU is in the open position/off, that the tails coming into the board are still live. So if it is a sub-board from the main consumer unit/supply, then isolating the origins of the supply to the garage board is recommended.
Then also you mentioned a ring final circuit, it would be rare to loose all power to sockets of a ring final, without the fault being at the board, as it would take a number of faults occurring at the location of both the last leg and first leg socket on the ring. Or a fault between these and the CU.
So firstly I would check that you have power coming to the board, if that is established, then after safe isolation looking at loose/damaged connection at the devices and busbars.
If no power at the board exists, then if there is a primary supply, you will then need to investigate there, again for tripped devices serving the circuit (fuse, MCB, RCD, RCBO, RCCB etc..), then for loose connection again, with the installation safely isolated.
NB: Ring Final Circuits are different to Radial circuits.
If you have a radial circuit? The fault could very likely be at the very first socket on that circuit. A radial does not a have a return leg to the board, so a fault at the first socket or a fault to the power upstream of that, will cause complete power loss on the circuit. A ring final, would require two similar faults.
