As far as brakes go I have LX cantis on my pompy so will they go on a bullhorn bar?
I use profile bullhorns. Very comfy. Used to run flat bar/bar end combo but spent all my time on the bar ends, so decided bullhorns would allow me to get the brake levers up where my hands were.
re brake levers, am I right in thinking that road bars are of a larger diameter (at the grip/bartape) than mtb levers?
Anyway, if not, regular MTB levers will fit but will put the cables out forwards and give you huge cable loops which will be horrible, both aesthetically and functionally. You could mount the levers upside-down to sort the cable routing, but it they might be a bit awkward to use.
The best best is to by TT levers. I run profile ones that fit in the end of the bar via expanding wedge, and the cable exits down the inside of the bar and emerges near the stem.
Not necessarily a cheap way to do it, but it's a very tidy setup. And as I ride far more miles on my commuter than on my MTB, getting the setup right seems worth it.