Bookworm,
I have only just fond this post however late. Please refer to the table in JAR OPS 1, Subpart D 1.297 "Application of Aerodrome forecasts (TAF's & Trends) To pre-flight planning"
This specifies when you should take wind limits into account and also when mean or gust is applicable i.e. Destination, Alternate, Enroute Alternate and ETOPS only etc for pre-flight planning purposes. of course a healthy dose of common sense will always keep you safest.
Regards