I could be wrong but I think the VAT on AC installation is still 5%. It might be worth asking the installer to confirm the VAT rate to be sure what you will pay come completion.
Those Mitsubishi units have a heat mode when looking at their documentation.
http://www.mitsubishitech.co.uk/Data/M-Series/MSZ/2019/Leaflet/MSZ-AP-VF(VGK)_Leaflet.pdf
Those Mitsubishi units have a heat mode when looking at their documentation.
http://www.mitsubishitech.co.uk/Data/M-Series/MSZ/2019/Leaflet/MSZ-AP-VF(VGK)_Leaflet.pdf