For details of specific canals and waterways, see either John Russell's UK Inland Waterway Size Restrictions in English Units or his UK Inland Waterway Size Restrictions in Metric Units
For visualizing narrow and wide canals on a map, see:
|Category||Tonnage (T)||Length (m)||Beam (m)||Depth (m)||Headroom (m)|
Armed with a large scale map of Europe showing the canals and their categories, one should be able to workout what routes are available. Be warned, as many French and Belgian canals may be only good for a depth of 1.8m not 2.2m. Usual problem of them not being dredged due to lack of money. (Thanks to Michael Clarke for supplying the above information.)
I'm told that maps by Imray might fill the bill. Please email me if you agree/disagree. I am told (12/2006) that Imray's "Map of the Inland Waterways of France" does NOT give the width of the locks or the Category of the canals.
Waterways World magazine suggests (4/09) that the definitive map of Europe's rivers and canals is the European Waterways Map and Directory from Euromapping. The map reportedly includes information on both beam and channel depth.
Some information, and a book to buy, will be found at Michael Briant's Routes Between the English Channel and the Mediterranean.
See also Noorderzon for (somewhat pricey) software.