Are there any photos or videos of the drones at Gatwick?
It is very likely that there were no drones, and this was a case of mass hysteria.

One actual crashed drone was discovered during the search, but that could very likely have been a hobbyist drone that got away, days, perhaps weeks earlier.  Lost toy drones happen all the time (even though it shouldn't happen near a major airport, it does...)

https://www.secretflying.com/posts/police-admit-it-is-a-possibility-there-was-never-a-drone-at-gatwick-airport/