Is he picking on you Tim?

Quite correct, we used our outside kitchen, bathroom, storeroom roofs for the panels (about 30m2). The cost was around €3000. Was promised some grant money but this never materialized.

I was advised against the heat exchange option as it can be costly to run.

I was also advised against 'floating balls' as they are simply a pain when trying to swim plus, on their own, they don't do very much - simpler to buy a summer cover. this is basically a very large, strong, sheet of bubble wrap.

And the latest one I just bought comes with an 8 yr guarantee. Australian company. The last one from Barcelona lasted 3 yrs and then turned brittle. Time will tell but it is very effective.