The QL Hot water cylinder on my 2005 B39 recently developed a leak which on investigation was a failed weld around the spigot for the engine cooling circuit. I was advised by Gosport Boat Yard when they tried to source a replacement that Volvo had announced at the 2010 Southampton Boat Show that the entire QL line is discontinued.
Although I can find no information to confirm this, even Clipper were unaware, I have found that the Quick Nautic B3 20 litre model is a virtual, like for like replacement if anyone else faces a similar problem. It is also a very similar price.