@Ripster, yeh I changed the heads valves when I bought the boat at 7 years old, will have to consider all the smaller ones soon.
Update to rudder damage - it dropped straight out and is really heavy with neutral buoyancy - might be as a result of water ingress however, the damage was a lot smaller than those photos indicated. A third party used my camera to take the pics and he must have been up really close. The comment from the boat builder when he saw it come out of the water was that most of the boats in the marina have worse damage to their rudders. Going to be interesting refitting rudder, shame there is no bolt hole at top of post to feed a mousing line through.