In Answer to the last point.
Just as there are game anglers, pike anglers, etc there are different canoeists and types of boat that they paddle.
Playboating - doing daft tricks on a wave often made by a weir or by a drop in the river bed. This takes only limited access to specific sites.
River Running - Testing yourself against the harder White water rivers. These guys often want more access, but are generally quite responsible and willing to work with anglers.
Slalom - If you want to go to the Olympics then this is canoeing for you. Against the clock on white water and against each other. This is what I do and love it. Again this needs limited lenghts of river as the courses are 90 -120 seconds long but do require lines accross the river for gates etc meaning that angling on that section is really not advisable. There are only a small number of truly excellent sites for slalom in the UK so co-operation from anglers is very much valued. BTW we got a silver in the last Olyimpic games in this so think of the good of the nation on this one.
Marathon /Sprint - This is mostly concentrated on the south of England, fast V shaped boats on flat water, tend to stay near their clubs, you'll know if you have a club near you...
touring canoeists / Scout groups etc - likely to be very occasional boaters, this makes them very hard to educate in how to co-exist happily with anglers and they are less likely than others to hold the correct permits, or be members of the BCU etc. Like the "child anglers" mentioned in another thread hard they are potentially hard to keep control of. All I suggest is to try and be tactful if you meet one of these, respect will breed respect in most people... we all hope!