This is increasingly untrue. RNAV/PNAV approaches are increasingly being flown - which are exclusively satellite-based navigation, and, at smaller airports, “traditional” approaches based on ground instrumentation are being phased out due to cost and inflexibility... potentially leaving pilots stranded in bad weather conditions if GPS fails.

They're definitely less safe without it though.

Also, I don't know about the UK's laws, but any sort of radiofrequency jamming is illegal in the US except in extremely extenuating circumstances (like war) that I don't think a roving drone would fall under.