For 'Intentionally or recklessly disturb any wild bird listed on Schedule 1 while it is nest building, or at a nest containing eggs or young, or disturb the dependent young of such a bird.
Fines
Penalties that can be imposed for criminal offences in respect of a single bird, nest or egg contrary to the Wildlife and Countryside Act 1981 is an unlimited fine, up to six months imprisonment or both.
For further information
For detailed information, it is advisable to consult the Act itself, which you can find on the UK Legislation website.
https://www.rspb.org.uk/birds-and-wildlife/advice/wildlife-and-the-law/wildlife-and-countryside-act/'
if I knew who you were, I would report you without hestation.