I have bought and sold my boat(s) there over a period of about 20 years, and watched many being sold. There are a few considerations - the main one being that there are some (but limited) lovely, reasonably-priced moorings with good support. So, if you can offer the boat with one of these moorings (of course the operator has to have agreed) then you can ask an above going price. Many folk selling their boat, who can afford to wait a while, thus tend to offer above normal and then hold tight until a really good offer comes along. Also, given the lack of depth and the distinct saucer shape, a vee-bottomed boat is preferable. Be careful about the width - 8ft 6" is really about the limit but even that will result in many scrapes - you spend a lot of time doing touch-up painting! Also check the state of the bottom - such a shallow canal does appear to cause more wear and so an out-of-water survey is absolutely essential if the boat is more than, say, 20 years old.