Its a few minutes walk from Watford Games Workshop, I couldn't find their website but its discussed here:
http://www.warseer.com/forums/showthread.php?224112-Looking-for-clubs-in-Herts-Beds-North-London
Havent been for a while but was always busy and friendly, its on a wednesday night. There is also a club in hemel, but they werent very friendly and didn't play much
40k.
Anyway this is not very useful if you dont have a car, so if you have any joy with clubs near Hatfield gimme a shout mate!