Many thanks, I have just replaced the spring on the heads door lock (Bavaria 33 Cruiser, 2006), the initial spring size mentioned was the exact size. Very easy to replace the spring, but reckon a slight word of caution on reassembly to ensure that the lock casing plate (as removed) is firmly fixed on reassembly and the holding tabs (as prised off) are holding the plate and are not damaged. This plate holds the whole latch/lever assembly in situ, which ensures that the door opens (or not). On my heads door, the fit of the lock casing is very tight to wood, so I'm not concerned.
In the cabin I can exit thro the hatch if the door latch fails, in the heads I'm too big to exit the portlight! I could install an axe next to the door.
A simple slider door catch would have been adequate in heads/cabins with no other exit route.
OK, all of this is OTT ............ but just a thought when you take the casing apart, I have springs ready to repair the next latches!