I was just re-reading this thread and noticed that Worksop was wondering what his bike might be worth as trade in. I reckon I can have a fair stab at that one having talked money with Streetbike recently. Big spoiler alert...
I guesstimate in the region of £5k for part exchange. Maybe 4.5k for a straight sale. However, considering the subsidy, you might get less. You would benefit from money off the new one though.
You might be able to get your hands on a 2015 SR for £9,500 with the subsidy, but I doubt that you'd get much more than 4,500 for your current bike. So the cost to change will be around £5k. I wouldn't bother with the 2016 SR unless you think you'll be running at 85+ down the motorway for any length of time.
As you're happy with your bike and only do 6k a year, I'd be tempted to keep it for another year at least. I think 2017 might bring a new controller, higher revs and thus more power and top speed. I don't know if they can extract more torque from that motor and arguably they don't need to. More power would be good though. It will help with acceleration over 60mph. Fairings or at least a decent screen too.
You might be better off investing in a super charger this year.