So bedroom 1's light worked even with the lighting MCB off? That's not good. You either have that lighting fed from a socket circuit or the downstairs lighting circuit. Turn other MCBs off one at a time and see what one causes the light to go out.
As for the earth wire earthing out on a bit of ceiling wood, that's a nonsensical statement. The CPC ("earth wire") is at earth potential, so can't "earth out", especially not to a non-conductive material like wood!
IF the CPC comes in to contact with a phase conductor ("live") then it would trip the MCB, is that what happened do you think?
There MUST be some reds up there above the light. The two blacks are the neutrals (one from the CU, one to the next light), and the single black is the switched-live coming back from the switch. There will likely be 3 reds connected together, one from the T+E to the switch, one from the T+E supply from CU, and one from the T+E to the next light. This is the most likely cause of your original, and current problem. Get up there and check!
It's possible that the fault has blown a connection somewhere. Start by removing and inspecting behind each ceiling rose (or switch if the looping is done in there), and check if there's any junction boxes up in the loft.
Work safely and good luck!
PS. A photo's worth a thousand words!
Stop calling circuit breakers MCBs
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