Best low or zero carbon tech for new house

I’m rebuilding my house and living in the wonderful borough of Guildford a constraint on the planning approval states I need to save 20% carbon emissions through the use of onsite zero or low carbon technology. Examples given include Solar PV, Solar thermal, ground source or air source heat pumps, or CHP.

I’ve tried doing some research but it’s hard to work out exactly which will be best as the calculations are complex and need lots of effort to get realistic numbers for each option.
On the face of it solar PV seems to be the best, however the house won’t be built before FIT stops.

Anybody have any recommendations, thoughts, insights?

Are there any recommendations for solar PV companies that serve Surrey? (PMs) welcome.