The UKA Rules for Competition include the following:
RULE 240 S 5 UKA SUPPLEMENT – HEADPHONES
“The wearing of headphones, or similar devices, (other than those medically prescribed), is not permitted in races on any single carriageway road that is not wholly closed to traffic.”
Wherever HDSRL races use or cross such roads, headphones of any description (except if medically prescribed) are not allowed. This is not at the discretion of the race organisers.