Looks like one of the old type outlets which were used for items such as clocks. Is it fed by grey twin+earth? If so it will be OK to replacing with a blank plate, terminating supply wires in terminal block.
I hate to bury live wires, so I just want to be sure that I understand what you're saying to me. This is a connector for a low ampage device (clock) fed by single core (phase) with a 1amp fuse, and as such can be simply terminated in a normal terminal block and left under the floorboards. I can see how that would be OK, but I'm still learning and want to be double-sure.
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