Complex sentence: They operated the artillery range at South Uist; this role was passed over to DERA (eventually to become QinetiQ) who still remain at the Benbecula and South Uist sites.
Split into simpler sentences: They operated the artillery range at South Uist. This role was passed over to DERA (eventually to become QinetiQ) who still remain at the Benbecula and South Uist sites.