The Open Guide to London: the free London guide

For some obscure reason probably best left to the bureaucrats who invented it, cyclists need a special permit to ride on canals. About the only thing that can be said is that you should read the Waterways Code and be courteous to other users of the canals.

The permit itself is available free from their web site and proves nothing in particular.

And yes, anglers are NOT supposed to block the towpath in any way.