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That looks like a transformer. Sometimes the wires are caught up on insulation or something else!
I use a lot of the EVOFire large hole fittings to convert to GU10. They cover the surrounding plaster which is almost always damaged when you remove the existing ones.
https://www.downlights.co.uk/fire-rated-gu10-downlight-large-hole-integral-evofire.html
There are smaller ones available which you add a plate to. Last time I looked the large ones were harder to find as I think they are moving over to the normal + plate to cover the larger holes.
There is also a version for insulation. They're rated for fire and bathrooms.
Are they any other removable items/panels/etc in your ceiling? In my bathroom you can only get at the connections by taking down the ceiling extractor fan.