Is dowsing legal and an accepted practice in the UK?

Yes, dowsing is legal. Dowsing or divining for water has remained a constant practise throughout British history, when other uses for dowsing were driven underground by the Witchcraft Acts. These weren’t totally repealed until the 1950s.

Some European countries are more open to dowsing, having not been affected by the Witchcraft Acts, and in Germany it is a process in planning permission applications to survey the potential site for geopathic stress using dowsing.

Health dowsing is legal, and the dowser can report their findings, but they do not go as far as pronouncing a diagnosis. Only the medical profession can do that.