Let me play devils advocate.
Your solar panel investment should repay in up to 10 years in the UK climate. After 10 years, there is every likelihood that technology has moved on to the extent that what you have on your roof is obsolete and you will need to pay to have it removed together with a further bill to make the the roof good. Do you think this will make the sale of a property more or less attractive.
Add to this further issues like ongoing cost of cleaning, breakages and maintenance of panels and electrics, removal of birds nests, weather damage, inability to get access and carry out repairs to the roof structure and collapse of installation firms during guarantee periods.
People should make decisions based on merit and not on slick sales talk.
We got in early and our 11 year old system costing £10k paid for itself in about 6 years taking into account lower bills. We now earn at least £2k a year in FIT payments plus all washing, tumble drying, dishwashing is done during the day when we are generating our own. As far as I can see, the only real advancement since our installation is in batteries which we'll be looking at shortly.