There will be hordes but most are respectful. If you don't spend at least a half day at the York Minster, shame on you. Since you haven't said what your primary interest is, start walking the streets and do some people watching. Get on the double-decker and see the town. Walk the wall. I'm sure you will find lots of opportunities for photography. The language is close enough to ours-talk to the people. Eat some 'pub grub', it's good stuff. Enjoy yourself and take your camera along. Take two camera bodies and two lenses. Don't take a tripod. One lens should do it if you take an 18-200 or 250. The second body is your insurance policy. Lots of batteries and I would suggest 16 mp class 10 memory discs. Have a great time!