Hi Adam, first of all, welcome to the LOC.
If I'm reading your post correctly, an individual bought the car from a Lexus main dealer last November, and is now selling it 8 months on. I'd wonder why?
If the car still has 4 months warranty is it transferable?
£11k would be a nice price to pay, but if the warranty is transferable, a 460 with 69k miles and full service history is worth the asking price.
A few 56 plate 460's recently sold for £10k but mileage usually over 100k. Bear in mind road tax of £500. Push and pull all the knobs, buttons and switches, anything not working guaranteed to be a few hundred quid to put right.
Recently sold my 460 after 4 years of ownership, they really are great cars.
Good Luck.
Graham.