PEAK domestic heat pumps tick all the boxes. Its the only system i specify to customers who appreciate a well engineered solution that is assembled here in the UK. 
It might not be the cheapest but its supplied as a package with pre-plumbed cylinders and installation assescories to insure continuity between installations.
Packed full of all the latest technology with reassuring extendable warranties and fixed price servicing. Larger rivals may compete on price but full short in many other areas. Get in touch for more info/case studies