Well bulls are always going to make you a bit nervous! Sometimes, the farmer will put up a warning sign that says 'Danger - Bull in Field' or something like that. However, many times, there will be a sign up saying that, and no bull anywhere at all in sight. I'm not aware of it being illegal to have a bull in a field with public access though.
The story mentions that they were walking through the field near darkness - I wonder if they somehow surprised the bull or something? Like they didn't see it beforehand. Not saying that it was their fault, but just wondering if it got startled or spooked somehow.
Sheep are the most common around here & really don't represent any particular threat - they are generally more keen to stay away from you, unless it's winter & then they sometimes think you are coming to feed them!
When we see cattle in a field, we always sort of scan about the field and make an assessment of danger & how we're going to handle the situation before entering the field. If we can, we will usually give cattle a wide berth & do things like taking care not to walk between a mother cow & her calf and stuff like that. There may often be other walkers about, and you can observe how the animals are reacting to them. If we see a bull that looks like it could be trouble (which isn't very often), we'll find an alternative route to be safe. Usually the male cattle that we see in fields are the ones that have been castrated, not actual bulls.
We don't have a dog. But if you're walking with dogs, I think it's part of the countryside code - you need to keep your dog on a lead & well under control, so that it doesn't disturb the livestock and/or get them riled up.
We have been cornered by cattle before (female) which kind of freaked us out, but they were really just curious about us & kept trying to lick DH! Eventually they lost interest and wandered away. We also got lost once & climbed over a fence into a pen of fairly aggressive swine - luckily the not entirely thrilled farmer was there to help us & got us back on track (and off his land!).
If it's just cattle (no bulls) and they're in your way, and there's no danger of upsetting them over calves or something, and you've got a walking stick - you can kind of wave that about & 'haaaa' them out of the way. We have done that before too.
So I guess the main thing is to just be alert and proceed sensibly with caution, whenever possible.