There are many more airports that have an RNAV GPS/GNSS approach procedure, than ILS. ILS requires expensive ground equipment, and fairly low obstruction clearance for miles surrounding the airport. I expect RNAV GNSS is used with some frequency at even big airports like Gatwick, on days when conditions don't require ILS in particular when the ILS is out of service for planned maintenance.

Example RNAV GNSS for Gatwick: https://opennav.com/pdf/EGKK/EG_AD_2_EGKK_8-4_en_2010-07-29....