Dropping someone off at UK airports can add up—expect around £6.51 on average,...

https://dlf-ne.org/is-paying-two-barrier-fees-ever-the-right-move-at-uk-airports/

Dropping someone off at UK airports can add up—expect around £6.51 on average, with Gatwick charging £10 and Heathrow £7. But pick-up fees can be different, so it’s worth checking both