Crucial facts that I have found from this User Guide that I have not seen clearly stated elsewhere are:

1. When using Timer 2 as a baud rate generator for serial port 0 in UART mode (mode 1 or 3), the timer works from the crystal frequency divided by 2, and CKCON.5 has no effect.
   
2. When using Timer 2 as a baud rate generator for serial port 0 in UART mode (mode 1 or 3), the baud rate is always the timer overflow rate divided by 16, not divided by 32 (or optionally 16 if SMOD is set). SMOD (WDCON.7) is ignored in this mode. I could not find this explained in the text - I deduced it from the block diagram.
   

I think these facts must be correct, because when I use them I find that the baud rate calculated matches what the chip actually does. Now I can get on with making it do what I need it to!

Thanks for all your help - Rowan