Hi Henry,

I have tried this in the past with a friend on a buddy pass. I have a relative who works for Delta, so I fly S3B which is a little better than a buddy, S4 priority, but still kinda low on the list. We planned a trip to Copenhagen, DK in July for a week going through London Gatwick (LGW). From my personal expereince, I have never had a problem getting into, or out of LGW. On the other had, my friend on the buddy pass, was able to get to LGW, but would not have made the list for the return trip and ended up getting a one way ticket. If you are already in NY, JFK has a lot of flights to Europe, so I would just try to get on one of those if you aren't too far down on the NRSA list (whoever gave you the buddy pass can tell you this). The beginning of July is a tough time to travel, especially due to our July 4th weekend. I'm not sure about European holidays also, but there are a couple websites that tell all the official holidays of each country. My advise would be to try from JFK if the Travelline says the flights are "fair", otherwise try to get to LGW. When you are at LGW, you can find some really cheap flights from there to other European cities on Easyjet or Ryanair or others...probably cheaper than a train out of the UK. There are a lot of good articles on the site explaning the Nonrev process so I would spend some time studying this site...especially ATL to Europe on DL. Other airports I have Nonreved out of or into are:
Frankfurt (FRA) - very busy airport...pretty standard as far as comfort is concerned. Once flight is ready, you go to the gate which is a separate room. You wait there until you are called along with the reserved seat passengers.
Stuttgart (STR) - pretty small airport and easy to get around. Delta has one gate with a bunch of chairs....not to comfy.

LGW is a really nice airport. It is big and busy, but has a lot of shops and places to eat....plus a bunch of comfy chairs with a screen showing all the flights coming in and out so you don't have to wait at your gate.

Let me know if I can help anymore. Good luck!!