[Occasionally6]

If it only displays two digits to the left of the decimal point and you can get over 100mpg coasting in neutral that would explain why the display goes to "---". That makes it harder to tell when/if the fuel is cut off completely. It may not matter much in practice though - either way, "---" is good.

Something else that I think we've overlooked is that this is a Multi Air engine. That is probably going to mean a rethink on some of the driving techniques. Because the pumping losses are reduced I expect it's going to respond more to Diesel appropriate techniques eg. gentle acceleration will probably be no worse than trying to get some load on the engine. Or at least there's less scope for improvement with it.

Lower pumping losses also might mean the DCFCO coast is more usable. The car will still slow of course but you won't have (literally) half the engine acting as vacuum pump and wasting energy.

If this model has the gearshift indicator are you using that? It will be interesting to see what feedback you get from the uploaded data too (if you do that).