remmebr just a DIYer , i'm sure the more Pro guys will make suggestions
you may need some tools - i have various tap box spanners that fit - but often wont go around the nut - because of the ceramic -
This i have used just recently on a small basin where the TAP had come loose a few weeks ago.
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BUT it depends on the Tap and how its fixed to the basin
some of the other tools i have
Fits 50mm A/F and 46mm A/F brass and nylon nutsNB: Some modern waste backnuts are slightly larger than 50mm and will need filing to fit and nut must be hexagonal not octagonal
www.toolstation.com
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A photo from underneath would help
hopefully it has an isolation valve