Wow, that's alot of miles..
I think I'd be gutted, but would probably put it down to experience and take it on the chin.
I assume you test drove the car, and was happy with it, and as you managed to do 440 miles is it not reasonable to accept that thing can and do go wrong, especially something of that age and mileage.
How long did you drive it for in an overheat situation? as it's unlikely it spewed it's guts without prior warning.
It is better to remain silent and be thought a fool, than to speak and remove all doubt!