Had a look at rhe current situation due to the recent posts. Price paid for electricity is down by a half. But price of an installation is almost halved.
The expensive panel manufacurers have gone out of business. Leaves the Chineses and Indonesians etc. Are their panels any good? Dunno.
However, it means more people can now afford an array and will get the same return %wise.
But I have a good situation.
Main difference is, your house has to conform to an energy efficiency standard now. Seems to be, loft insulation, double glazing, cavity wall insulation, condensing boiler. (Level D or above)
The rate paid to early joiners is £0.455p/Kwh from April 1st with the RPI rise.
Bit here on amount installed, number of installations nationally etc.