So I stuck it on the rollers to break-in the engine

Initially it brought up the problems with cooling, there was a huge airlock in the system as a result of the electric water pump.
So I pulled the thermostat, removed the mechanism effectively leaving a restrictor disk. I've been told that this may not be good as there are different coolant routes through the head depending on the coolant temperature so I may have to revisit the this later - I'm hoping that the flow of water will be enough that its just going to be flooding the passages with a flood of water.
Yesterday I gave it about an hour break-in, (2500 - 3500 rpm with a medium load on the rollers) the highest water temperature I saw was 98degC.
Once I can get back on the rollers I'll start mapping it. This is going to be a few weeks off yet.