Ok, it's now been just over a week since we've had it all installed. The weather compensation curve has now automatically dropped down to 2.1. Really happy with the upgrade. Boiler flow temps are regularly under 40-50 degrees, and if we do require a boost, the system is much more responsive. The app isn't the best, so not sure I can recommend the additional expense of the SensoNet gateway, but it'll be handy in the future.
We reduced the HW heating to 90 mins in the morning, and asn hour in the evening. Not noticed any loss of HW yet (although just two of us here).
At some point, would like to introduce TRVs into the mix to try and increase the efficiency further, but that's another can of worms!