30W - Agree.. That's why I wrote in the terms I did!
LGW is more difficult and also relevant to that point is what aircraft you are flying (can you use the smaller fields such as SOU etc) . Folk do forget too that often diverting from the hold wouldn't be using as much fuel as from the G/A. Each scenario is different, and that (for me!) is what makes it interesting. But if you haven't enough fuel, use the distress call - its what it's there for!