By coincidence, we have just been through this process. Had a full survey, have a south facing roof, no tree shade, room for battery storage etc. Three quotes for varying numbers of panels, with or without battery. Between £6.5 and £11k. Sat and did a evaluation and read it through carefully, and it worked out at between 8 and 10 years payback. We have decided to postpone the idea, and spend more money on further loft insulation, and other measures to cut our heat consumption instead. I suspect (hope?) that there may be more help coming with a Labour government green energy initiatives so we will hang on and see.