I have lots more questions about other aspects of the heat pump, but I think they need to go in a new thread!

I do have a difficulty with the balancing as the upstairs bedrooms and landing are getting a little warmer than I would like. Gradually tightening down the lock shield valves but may need to resort to using the TRV's as maximum limiters.

Anyway:

1. I can confirm that my noise level was mainly caused by the primary pump and reducing the flow rate to the flow rate recomended by mitsubishi reduced the noise considerably. From 26 Lpm down to 19Lpm

2. I increased the secondary pump flow rate to 1.1Cmh (19Lpm) and achieved the flowing temperatures across the buffer:

This seems more like what it should be so I am going to leave it at that for now until my installer arrives.

Whats a little bit concerning for me is the drop in temperature between the top two ports meaning from the heat pump flow across the buffer to the radiator circuit. In the example I gave it was from 40.0c to 36.7c = 3.3c difference whereas your example is 32.7 to 30.8c = 1.9c difference.

However, I haven't finished adjusting the secondary pump speed yet so that may make a difference. 

Sorry @grumpidoc, we appear to be hijacking your thread. Hope the previous suggestions have helped.

Due to the low outside temperatures, my ecodan is going into anti-freeze at night when the set back means the ecodan idles, and in De-frost mode for most of the day. All expected so no issue. However, after each de-frost the ecodan ramps up to recover and this is making temperature readings from the buffer problomatic.

So, at this stage I have focussed on the noise issue and simply reduced the wilo secondary pump speed to the radiators to "can hardly hear it". The Wilo speed dial is still within the recomended range. This noise reduction is especially necessary at night at the moment as both circulator pumps run during the anti-freeze mode, even though the ecodan in set back is idle, to stop the pipes freezing up.

All rads still warm.

I will still monitor the buffer temperatures but wait to draw any conclusions.

I was trying to highlight that my buffer tank is plumbed in differently. Your secondary circuit flow is through the lower, colder, part of the tank so it will never get as warm as the primary flow in the top of the tank. I've got my secondary circuit flow from the buffer slightly warmer than the return flow to the heat pump. I have to wonder if your buffer tank (and probably plenty of others) is plumbed in sub-optimally.