A friend and I did say something to a group of children at the Dulwich Wood House who were using sticks to bang on a bin by our table, pretending it was a drum and deafening us in the process. After a few minutes of frenzied drumming which was drowning out our conversation we did think it a bit much!
We got a bored look from the parents who had been trying to ignore the whole episode anyway, and finally a 'yeah, alright' followed by some dirty looks when we asked them if they could deal with their children. At least they made a half-hearted attempt to acknowlege our situation because at the time we did feel we were likely to get some aggro. Would've been nice to get an apology but that was a bit much to expect.
Good, I am glad you took a stand. I think the old English reserve of grinning and baring with it does not help. The issue is with a small minority of parents who become both verbally and physically abusive. That's where the landlord/landlady should step in.
When I was young (just before I was sent up the chimney's on my day job) my parents had no problem with adults telling me off for being loud etc if for any reason they happened to be out of earshot. My, how times have changed.