Dropping someone at a UK airport can cost £6.51 on average, with Gatwick...

https://jeffreysbestjournal.opalvector.com/posts/what-should-i-check-before-i-rely-on-a-free-long-stay-drop-off-window

Dropping someone at a UK airport can cost £6.51 on average, with Gatwick hitting around £10 and Heathrow about £7