We've got solar thermal panels for hot water. I haven't done the sums yet, but last year (2008) we barely turned the boiler on from May, June & July ... and then it rained all August. We've been getting lots of hot water since March this year too. Once I get time to go through the bills and get out my calculator I'll report a bit more.
We've also got a Hwam wood burning stove in the living room. It's a free standing one, which looks fantastic, as well as kicking out enough heat for us to turn off the radiators on all but the coldest days. I'd love a back boiler too, but as the woodburner is at the opposite end of the house from the cylinder it would involve a lot of upheaval (and we'd probably have to swap the cylinder for a thermal store).
If you get solar hot water panels make sure you quiz your installer on how it will work with your plumbing. We turn on the hot water much less often now, so our towel rail which heated the bathroom is never on when we want it.
It took us some time to work out how to get the best from the panels. In summer, we turn off the boiler completely, and only turn it back on if the temperature in the cylinder is too low for a shower.
To get the best results in winter we installed a new programme clock for the boiler, so we can control the central heating independently from the hot water. That means we can have the heating on first thing in the morning, without heating up the water cylinder, so if it turns out to be sunny we get the greatest benefit from the solar heat.
For more of my tips please browse through my blog posts by clicking on the link at the top of the page.