The Solar Trade Association has done new analysis that shows that the UK has now reached its 1 million solar homes milestone if you count both solar PV and solar thermal.
Recent statistics released by DECC  show that there are now 800,000 homes with solar PV electricity panels.
The solar trade body also estimates that there are 250,000 homes  that have solar thermal hot water heating panels.
Putting the two solar technologies together that makes over 1 million solar homes in all.
Leonie Greene, Head of External Affairs at the Solar Trade Association said:
“DECC’s latest data proves the British solar industry can deliver the large volumes of clean power we need, and fast. However, the data also shows relatively poor levels of deployment of solar on larger buildings like schools, factories and warehouses, where this technology is particularly efficient and cost-effective. We are very concerned that Government policy is now severely constraining growth across these prime rooftops. Worse, there is effectively no meaningful support now in the UK for solar schemes over 1MW in size. That cannot be right.
We hope that Government will heed calls from right across the energy sector to get fully behind solar power again. Solar sits at the heart of a modern power system so the UK needs to channel precious investment towards clean technologies that can best secure our future.”
Latest deployment data  shows that larger solar rooftops are only 10-15% of the market, much less than in other European countries. The STA is keen that this sector is allowed to grow to its full potential. The data also shows that the UK now has 9GW of solar PV in total, according to official statistics.
This milestone has been reached just as the solar revolution is taking off worldwide and yet coincides with major cuts in support to solar PV in the UK, as well as the Governments proposal to hike VAT up from 5% to 20% on residential solar PV and solar thermal. 
Notes to Editors https://www.gov.uk/government/statistics/monthly-small-scale-renewable-deployment  There is no official data on the total number of solar thermal homes as many were installed before the Renewable Heat Incentive, but we estimate that there is 775,000 m2 of solar thermal in operation in the UK (see also this report from EU trade body ESTIF). Using a standard assumption of 3m2 per domestic installation, that gives 258,000 homes.  https://www.gov.uk/government/consultations/vat-changes-to-the-reduced-rate-of-vat-for-the-installation-of-energy-saving-materials  https://www.gov.uk/government/statistics/solar-photovoltaics-deployment