I had a random thought recently.....
You enter a station in a small ship so get assigned a small pad.
You then buy a big ship.
It obviously can't fit the pad you just landed on and I've never been told I can't buy a ship because of the pad size I arrived at.
I have to assume that you get sent to a larger pad elsewhere in the station.
Sigh... I'm going to have to test that now, aren't I?
Unless someones already done it?