I’ve started to hear good reports about British Gas heat pump installations (yes I know 
I can hardly believe it either).
They partner Samsung as well as Daikin and Vaillant.
My personal experience with a Samsung HTQ R32 has been excellent (local installer, who doesn’t serve E. England 
). Might be worth talking to BG to see what price they could come up with, either for a Samsung HTQ (2-stage compressor so a competitive CoP) or their newish R290 series (back to single stage compressor 
maybe just different refrigerant properties allowed this…)