Taking MtB's advice, here are some details of my issues.
1. The boat is very very difficult to cold start - it seems that heater plugs are working. It has been suggested to me that this could be a fuel injection problem (although injectors had major overhaul last year). Could be connected to point 2. Once started, engine runs fine if a bit smokey.
2. A lot of rust particles collecting in fuel filter - presumably from tank. Tank needs cleaning. If some of these particles have got further down the line could this cause injection problem.
3. A lot of fluid is collecting in the bilge each day - seems to contain water with some fuel and possibly oil. No obvious leaks detectable to me other than possibly from calorifier but this would not explain volume or nature of fluid.
Any help on who might look at engine for me in Long Eaton / Kegworth area gratefully received.