I had solar panels at the old house at the old rate and with a grant. Not sure if it's worth it now

Debster - it's more about future-proofing than making a fortune on the FITs (and, let's face it, a lot of the reason electricity bills are so high now is a lot to do with our power companies being owned by foreign companies and the huge FITs paid to early adopters and those companies who put them on people's roofs for nothing except the FIT profit).

Something that (at today's prices) will break even after about one third of the system's life (before factoring in electric car usage in the future) has got to be a sensible way to go, given how electricity prices are predicted to rise, and the poor return on investments currently (no pun intended).

Now that panels have individual optimisers, system outputs are much better than in the past, and battery storage can cater for usage when the sun isn't shining.

Which company paid your FITs? We usually use smaller electricity companies who don't offer a FIT scheme, so will have to have them paid by a different company, which is good as there will be no way we can be paid less than the 'deemed' 50% of total generation return to grid, even when we are (eventually) forced to have a smart meter.

It's still 20.5°C at 8.40pm.

Ridiculously warm yesterday, I agree!
We've had solar PV for some years now, and love it. Quite a lot of the time we use high consumption equipment (eg washing machine) during a sunny day now, rather than on the Econmy 7 tariff overnight. And I've just bought a plug-in hybrid car - and have yet (after 6 weeks) to spend a penny on petrol.
Most PV panels are installed on roofs, which may be good, or not - depending on the slope and direction of the roof. Where you are dictates the optimum angle of the panels and to some extent where they should be aimed. If you have outside space, you should consider a ground-level frame which may be preferable to a roof installation. Also, go for the highest power generation you can; when we had ours installed the maximum was 4kW.
It doesn't matter who pays the FIT; we were with EDF when we had the installation, but have changed supplier a couple of times since then - however EDF still pay the FIT (so far without error, touch broomstick!).
Lastly, not all solar PV panels are created equal. Somewhere in the Australian outback there is a setup containing all the major manufacturer's products, and you can see their output in real time, together with a graph of their gradual degradation. (Google should find it.)
I'll happily try to answer further questions if you have any!

PS - there are now gadgets around which will divert any excess power generation into heating your hot water, or into a battery. You still get paid the "deemed" rate which assumes that the excess goes back into the grid!

Thanks for the info Tim.

Batteries are still around £1,500 for 3.3kWh and 9,000 guaranteed charge cycles, and that's the one thing we are still unsure about. We could have a battery ready system, and add on later.

We already have solar thermal for water, so no mileage there at present.

But, panels now can have individual optimisers, which means every panel contributes its maximum, and is not held back by a poor performer.

Does your inverter make any noise?

The inverter is completely silent. However I do go into the loft on a monthly basis to check it's still working. A couple of years ago we found by chance that it had developed a fault without our knowledge, and missed out on probably three months of free power.

The one thing I don't like about any of the new (now available) inverters is that they auto-feed output to (a) the installing and (b) the manufacturing companies and they know you have a problem before you do. This means that you get a package through the post of the part(s) needed to fix the problem, and someone contacts you to fit it.

Given that the warranties are now 20-25 years on all parts, the chances of both (a) and (b) companies still being in business by then is practically nil (particularly with the FIT scheme ending in March 2019), so what happens to your data and access to your system?

Presumably they also know when you are not using any of the power you are generating and so know that the house is empty (a bit like Smart meters). Which doesn't please me greatly. And there doesn't seem to be any way round it.

I was with Npower