With all the canals are there places to rent kayaks? I couldn't find any online except clubs.
The only place I saw people on all kind of water transportation was on the Thames River. We house boated between Oxford and Henley. We started out in Benson on the Thames River. If you google River Thames Kayaking or River Thames Kayak rental, you will find lots web sites to look at. I saw they have trips both right in London area and up river. We rented narrow boats on other canals, but did not see the variety of boats water toys like we saw on the Thames.
A few years ago (around 1997) my family went canoeing along the Wye near Ross-on-Wye. Not sure this is the same place that we got ours from but it seems to be what you're looking for: