Yeah theres a good point right next to the Taxi way.
The car park that is use when the Ingleston market is on.
Approach EDI via the normal acces road, as if you were going fora flight. Take the fist left on the Last roundabout before enteringt he EDI complex.... folow that road down and turn right..... you'll see the open space from there on and its easy after that.
If your unsure.... tell me and we can arrange a meeting time and location and I'll show you.
I'm going fairly early to make sure I get a spot. LOL