Thanks for the replies.
Though we're most used to exploring new cities on our own (with guidebook) I suspect we'll enjoy the guided walk very much. I think it's great that such a thing is provided. Does one tip the guides, by the way? About how much? I'm just not sure what custom is for these sorts of things in the UK.
(Does one tip taxi drivers?)
Sue-- we'll be arriving at our Bath hotel late afternoon on August 5, so the extra tours won't work for us. I just hope we won't be jet-lagging so much that we we'll miss the Saturday morning tour. I'm hoping to do that, have a pleasant simple lunch somewhere (where?) and then spend the afternoon re-visiting some of the things we liked best on the morning tour.
Thanks again to all.