If you have pigeons roosting under your solar panels in the UK, there are a few things you can do to get rid of them. One option is to use a bird netting system to physically block them from getting under the panels. Another is to use an ultrasonic bird deterrent, which emits a high-frequency sound that pigeons find unpleasant and will keep them away. You could also try installing spikes or other physical barriers on ledges and surfaces where pigeons like to perch. Finally, make sure that there isn't any food or water available for the pigeons near your property, as this will attract them and encourage them to stay.