In April I flew on NW from LGW and had no problem getting into the Continental lounge. Quite nice, with a good view looking over the runway and aprons. I am a Plat though so it could be a bit different with your Gold card. I would take a print out from the internet that says you are entitled to lounge access when flying on an international itinery on a Skyteam airline.

Taken from KLM website, the Flying Blue page:

As a Flying Blue Gold member, you are recognized as a SkyTeam Elite Plus member* by all Skyteam airlines which offers you and your guest access to all our airport lounges, so that you can rely on comfort wherever you are.
In addition, with Gold membership you earn 75% more Flying Blue Award Miles when flying on SkyTeam airlines.

* Flying Blue members residing in the USA and Mexico are recognized as SkyTeam Elite member