There have been several qquestions regarding rules and etiquette recently. I recommend the RYA Inland waterways handbook. It is a must have "bible" for anyone using the waterways, and in answer to your above question, I quote page 25 from the afore mentioned book, "When approaching a bridge or other narrow section, slow down well in advance. If a boat coming the other way is nearer, wave them through first. Keep right until they are clear. On rivers, the boat coming downstream has right of way". I would also recommend taking the RYA Inland Waterways Helmsman's Certificate course.