My mother just came back from the Cardiff assembly, she went for a day the 1st week and 2 days the second week.
I was amazed when she said there were around 3500 the first week and around 4000 the second (including the Welsh congregations).
Just 4 years ago when we went to our last ever assembly the total was more like 10000. That's a 25% decrease over 4 years.
Not sure what the baptism numbers were though.