Price seems OK - my next door neighbour just bought a late 2011 ES CVT for £5,500 in a private sale. It's only done 19K but he's the 4th (might even be 5th - the seller had been left the car and didn't want an auto). I think they agreed the price based on what it came up for on WeBuyAnyCar, so that should be its worst-case value.
So a much newer ES Plus CVT, from a dealer, with 3 services (say £750) sounds perfectly reasonable.
On the 16" tyres, there's quite a lot more choice now than there used to be, although they are going to be a bit dearer than 15". I note Michelin do them now, and they didn't when we got our first EX in 2009.