No, because it is trivially insignificant. If every house in the UK went to solar water heating tomorrow it would have a negligible effect upon world greenhouse gas emissions. Indulging in posture politics and switching off brain as soon as "global warming" is mentioned simply distracts from the real problem which isn't in the UK or capable of being solved by the UK.
No, because the solar supply is unreliable - you still need conventional water heating available. If you switch off the boiler for the summer and rely upon a daytime immersion heater for the times the solar water heating is inadequate the small saving it makes is wiped out in a few days.
Try not to be a prat all your life.
Actually, yes, nearly all the examples shown are pretty awful. Not all roofs are dull grey.
Possibly, but we are talking about retrofitting today - not built in tomorrow.