You being serious? just because theres rust on the boot lock means the car is riddled with rust?
My boot lock is rusty because someone tried to get into the boot with a screwdriver and failed and over time its started to go a little but the rest of the car is as fresh as it came out the factory!
On the other hand id offer him £250 drive it off you can pick up an interior for about £50 with carpet and a steering wheel for about £30
Power steering could be an issue knackered pump being the hardest and a simple belt change being the easiest.
Mot and tax is a killer as it could have more issues than the owner says! worth a punt you could always strip the engine!
Thats a shitter.
I got mine years ago, it was mint and only cost £400.
Punto Gt no more!