I’m sure I’ve read somewhere that Samsung pumps don’t like going down to temperatures in the 20s so the 32C at the upper outside temperature end might be the limit. Other Samsung owners will able to advise.

I'm new to heat pumps and have only been experimenting with mine for a few weeks but I think that how efficient my Gen 6 Samsung is with low temperatures is linked to the flow rate. I don't have a PWM pump, mine has 3 speeds, and when I reduced it to speed 2 I have been able to reduce the temperature to the high 20's without the efficiency dropping off significantly, on the 3rd speed it was dropping off in the mid to low 30's. I haven't experimented with the 1st speed. With a PWM pump I have read that it isn't affected and I think the Gen 7 has the pump built in to the outdoor unit, which I would assume is fully controlled by the samsung controller.

I could manually latch the two zone valves open

Thats not at all silly (actually its very sensible), so long as you disconnect the feed to ensure you dont risk burning out the motor. 

What do you actually use the Hive for and would this defeat it?

They installed two rubbish neomitis thermostats. I didn't want two zones. We're in a small bungalow! The main zone is the whole house, zone 2 is just the two bedrooms!

I could manually latch the two zone valves open🤔.

I can’t recall if you said which rooms the Neostat controls. Would it matter if those rooms were not set back and it was permanently set to 19C.

You do need a way for the system to permanently keep a minimum of water volume and having any external thermostats, never mind two you’ve been given, might be unwise. Do you have a buffer at all? Your manual will give the minimum volume assuming you’ve been given one.

Sorry but there is no way I can tell from the photo what they are doing/controlling and there are several possibilities.  Nor can I tell whether connecting the signal lines together will work or where in the house the zones correspond to (and thus what you might want to do with them - basically why are there two zones anyway?)

However what you almost certainly want is both valves permanently open, and the hive (set a couple of degrees above the target temp except when you want a setback) simply telling the heat pump whether to switch on or off, via the relevant signal input to the heat pump controller.  Indirectly telling the heat pump to switch off by closing off the water circulation route completely (which is what will happen if both valves are closed under instruction from the Hive) is NOT a good idea, heat pumps do things like run anti-seize programs during summer or if switched off for a long time, and anti-freeze programs.  Some also 'sniff' the flow temperature when off by running the water pump for a minute or so, and during defrost you need the pump to be able to call on the water in the system, even if the house is over-temp.   

The call for heat contact on the Samsung is probably zero volts, not 230V, depending on the what hive does (which I don't know) you may need a relay.  Alternatively you may find it simpler to use an alternative way to do whatever you actually do with the Hive, basically they aren't particularly designed for use with heat pumps and heat pump controllers are designed to be the principal, or indeed only, system control so there is possibly a bit of over-engineering here.  Samsung is, however, one of the less feature rich controllers so it is possible that there is in fact something that the Hive can do which the Samsung controller cant.

I hope that helps, feel free to ask for further clarification.

I've adjusted them to 15/30, -2/43

See how that goes.

There seems to be three valves see pic

Can you confirm the implication that you have two zone valves and a diverter valve (three in total) and are you sure both hive and neomits stats are connected to zone valves not the heat pump call for heat input.

What area of the house is zone 2?

But confused by your abbreviations above. How do they relate to the four figures I've quoted?

14° -  -2°  

32° -  45

14/32 ( the high outdoor air temperature end of the wc curve) is what I'm suggesting should be 15/30 or 20/25, but 14/32 is probably OK albeit a somewhat higher min flow temp than you probably need when it's 15/16 outside

-2/45 ( the low OAT end of the wc curve) is what you need to adjust when it's cold.  Leave -2 where it is and adjust 45 down until house is just right when all external controls are calling for heat continuously. 

But confused by your abbreviations above. How do they relate to the four figures I've quoted?