Thanks for the advice all

and thanks for that link Maz, some useful stuff there.
I've been doing some more Googling. Apparently it is legal to keep a Bull where there is a public right of way but only if with cows (subject to age/breed restrictions.)
There doesn't appear to be very many cases of Bulls actually attacking the public, although it's hard to weed out all the pitbull dog attack type stories.
I think I'll continue to cross fields that contain Bulls,but if they're close to the path then I'll wait untill they've moved away.
It's worth knowing that cows with calves can be dangerous, I hadn't realised that and most of the cows on my local jaunt have calves with them.
Maybe I need to carry an old McDonals wrapper with me to wave as a reminder of our respective places in the food chain
