The cheapest answer changes completely depending on whether you're dropping off, waiting on a late flight, or jetting away for a week. Pick the airport and your situation.
Airports use confusing names. Here's what each one really is, so the recommendations make sense.
A car park (usually mid/long stay) where the first 10–90 minutes are free, with a shuttle to the terminal. The cheapest legal pickup — ideal for delayed flights.
The kerb right outside the doors. Fast but charged per visit (£5–£10). Cameras read your plate — you pay online later. No waiting allowed.
Short = a few hours close by. Mid = a few days. Long = a week+, furthest out but cheapest per day. Always pre-book to save 50–80%.
Hand the car over at the terminal; a driver parks it and brings it back when you land. Most convenient, priciest — pre-book only.