Welcome aboard Mick.
That spreadsheet of actual output is really valuable to show the vaguaries of the British climate. You can't get data like that out of any of the estimation programs, or decent weather info in most places either for that matter. I'm sure it will be a help for people thinking of battery charging and off grid living too.
One little request is that you put the panel size, number etc on the spreadsheet so folks don't have to search around the blog for it, thus making it easy to factor for other array sizes.
Your interest calculations are interesting. Something you might give a reference to is the maintenance cost, insurance, inverter replacement cost etc, and perhaps more about the realisable value of the actual electricity generated.
You may have covered this elsewhere, I will have to read more of your blog this evening.
Thanks Baz. I left maintenace out of my calculations believing that as I also left out any grid supplied power they would balance out. My insurance company has not increased my premium to take account of the solar panels so that isn't a problem and I figured that if the inverter needed replacement in 5 to 10 years I would deal with that if and when it arose. I'm not too concerned as in the time my system has been running my particular inverter has reduced in price so if that trend continues I don't see it as a major event.