Job done!

This is our new hi-tech garage. We now have zero gas consumption, but last might had roasting hot water and radiators all provided by heat exchange system that extracts heat from the ambient air and uses it to heat all our domestic hot water and all the radiators. - totally green and consuming no purchased energy whatever.
Return on investment will be approx 7 years, which is a sight better than money in the bank earning negligible interest.
Only problem is that all the kit and caboodle takes up a fair amount of space in the garage and necessitates a major rethink of where to keep all my junk and tools etc.