It's £400, there is something wrong with, yes, the milage, i don't think so. Paint work is cack and it has some rust, that's probably why they want rid or some other genuine reason. I'd say go and atleast have a look, good turn out to be a bargain.
You say it's only done one MOT in 5 years..surely that's a sign that it's not covered many miles, atleast in the last 5 years.
Any way you could always make your money back breaking it..