I think for an extra £30 or so per month i'd be going new over a 6 to 9 month old car.
On the older car, tyres will be needed sooner, mot due sooner and your warranty will end sooner. All these costs should be factored in.
With personal lease, how soon you have to take the car will depend on whether or not it is in stock. Both mine have been factory orders, first one took 3 months, the next one arrived in about 7 weeks and they held onto it for me for an extra 3 weeks.