Beehive at Oldfield Free Church is great (Malden Ave). Although they have a waiting list. Might be a good time to register though as lots of kids have left to go to school/nursery. They meet Fridays.
I'm pretty sure there is a group at Holy Cross too. I didn't go because it clashed with something else.
Also Barnabas Church has a group on. Tuesday morning, much smaller, no waiting list. It's just over the the Greenford/northolt border. I think the road is The Fairway.
Also, your daughter might be too old for this, there is a new baby club at The Visitation church in Greenford Broadway. The lady who runs it is great and will advise OU of lots of local groups. It's a bit tricky to find, down the step, through the blue door. That's on Monday mornings.
There used to be Stay and Play at the Children's Centre near Greenford Broadway. I never actually went but they were always trying to get me to go. It looked good, but just didn't work with school pick ups.
Have been to Stay and Play at Horsenden School Children's centre. Is good, but tends to fill up very quick.
The ones in churches are not religious.