Anything is within walking distance if you're willing to walk...
Anyway here's where it is:
https://maps.app.goo.gl/YZKPXp7LSjc5jPot5
Turn on satellite view and you can see it is on the edge of the long stay parking. I dunno if you're realistically going to save a lot of time unless your parking space is right at the back of the long stay car park. Worth it if it's free! I assume it's overpriced though.
From the map. It looks like the train is closer to the terminal :)
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