Meeting UK's solar targets will be a "massive stimulus" to the economy finds new report

As for cost to support you from anecdotal evidence.

My own recent purchase puts current cost of panels at approx £150 per kWh. £200 with shipping

Modern panels have a expected life of 20 years where they are expected to be at 95% efficency. Much longer at lower. So let's be Conservative and assume new panels every 20. Even though there is likely another 10 years where they are still usefull. Maths wise ignoring it likely matches accidental harm or acts of mythical fairy man.

25% production is a reasonable estimate of expected output for all cental daylight hours based on 8 hours a day over the whole year.

So in 20 years 19400 hours of daytime × 250w is 4850 kWh

Translating to 3p per kWh 4p with shipping but that goes down when buying in bulk. But lets say 4p based on diy mounting and cleaning costs. I'm on a boat for this project.

Vs average domestic power costs currently at 27p per kWh

Diesel is a max of 10kWh per litre. You ain't gonna get that and ignoring equipment costs likely close to equal to solar. That's likely an average of 10p per kwh for most domestic users.

And dispite media bull.

As a genral rule. Government spending helps the economy. Heck even mp expensing duck houses. While criminal and wrong gave one or more person a temp income. The only question is how efficient specific forms of spending are to economic boosts.