@WansteadClimateAction @pvonhellermannn @markhburton heat geek are very good and provide software to installers to facilitate affordable installs, they offer guaranteed efficiency levels for different costs - search “heat geek zero disrupt” to find their form and get an indicative quote, it might be less than you expect compared with others.

@sean they also removed VAT on it fairly recently (as in, the last few years) I think.