Results are in:
Set 11 Copper Marans (first year hens), 9 hatched, 2 dead in shells = roughly 80% hatch. Good.
Set 6 Exchequers: 4 hatched, 1 dead in shell, 1 empty = 80% of viable eggs hatched. Good.
Set 4 Welsummer. 4 hatched (and 3 are girls) = 100%. Good.
Set 5 x Light Sussex. 1 hatched. 3 dead in shells, 1 empty = 25% of viable eggs. Bad.
So taking out the sussex eggs, well over 80% which I am well happy with,especially given that the marans are only a year old. The Light sussex eggs I have been setting are from one hen only. She lays a darker but much stronger egg than her sisters and I've been trying to cultivate that quality. However, previous attempts have resulted in lots of dead in shells and anything that did hatch has been a cockerel. So obviously that is a dead end which is a shame. She is a hybrid strain and all the others I bought have either died or are laying porous eggs after 18 months. Not overly bothered as I have bought in some trad strain pullets last year and this year to replace them. I'll give up on trying to hatch from her and start hatching from my new birds when they are older.
So, overall, a great result, skewed by one bird with a problem. Taking out the sussex and the empty exchequer, I've hatched 16 out of 19.
I did have to break out 3 of the marans but they are doing fine and I feel this is down to the octagon drying them out too fast. So, that's the next thing to sort. Dry hatching it is in future.