That one's a 125 with 15,000 miles on the clock.

The cheapest GT on there (it's on Bike Trader too) is also a 125 at £1500 and that has some scrapes on one side.
There's a 200 in London for £1500 but that has 17,000 miles on the clock. Knock 10,000 miles off and that would be a good price.
On Bike Trader the lowest price GT200 is an '05 reg with 14,000 miles for £1900.