Use of live decoys is banned under the Wildlife and Countryside Act, and then 'allowed' under certain special circumstances
Part 1, Section 5 of the Wildlife and Countryside Act 1981
(1) Subject to the provisions of this Part, if any person—
(a,b,c)....
(d) uses as a decoy, for the purpose of killing or taking any wild bird, any sound recording or any live bird or other animal whatever which is tethered, or which is secured by means of braces or other similar appliances, or which is blind, maimed or injured; . . .
(...)
he shall be guilty of an offence.