Hi Claire - I'm currently trawling my way through the Stockton BTs; wish I had thought to post before I started so I could have saved others a lot of work, but a bit late now as I'm on p.85. As you say, it makes the eyes go funne - but it is so interesting.
One set which are really poignant are the Sunderland BTs for 1831/32 which chart the deaths in the cholera epidemic of that year. The clerk noted in the margin the first death from cholera, and then you can see as the number of deaths gradually increase and whole families were falling victim within days of each other.
Regards,
Chris