Yes, I’m in Kidderminster It’s the only Acond unit in the sea of Valliant 
Interesting stats, I’ll have to have a look into this comparison tool.
For a reasonable amount today mine has be using circa 500w and COP 4-4.5 which Is alright. Like you say always room for improvement.
It was Dec last year and a Sunday, so that why I ended up with pex, it was a long day that day. I was aware of the 22m pex internal diaamter, but thought it’s going to better than 15mm trying to feed 9 rads. It was kinda on my summer list this year to look at replacing the pex but ended up replacing the external insulation as it was zip tied and had pretty large gaps in it.
I have thought about moving the entry point of the pipes from the attic to the airing cupboard (which they go past), as this will half the exterior run and also take about 3-4 meters out of the heating run.
Downside is it’s pretty cramped in the airing cupboard already without try to drill through and fit 3 way vales as well. However it would also bypass the 100L buffer tank (however the installers have said removing that would invalidate the warranty), but they quoted me £500 for a service anyhow so it’s like 6 years and it will pay pretty much for a new pump.(but that’s another can of worms).
I did come across some 35mm external insulated bendy pipe which had the same internal as 22mm copper, but that was ££££ and probably overkill.
Never really thought about upping the main runs to 28mm, had considered 22mm. Wonder if any negatives of running 28mm. I will have to get watching some more heatgeek vids and work out watts required and pipe sizing for the runs.
Thanks for your reply and thoughts, appreciated.