While there's no doubt that the Peugeot 505 was an excellent family motor, they haven't quite reached the status of a 'nailed on' classic... yet. They are, however, an extremely rare modern classic and come to market so infrequently that getting a steer on prices is difficult. While we can't specifically value your car, we can tell you that we saw a 505 GTI advertised recently for around £2750. The very best examples of the breed can go for around £4000. So you need to decide if you think that the cost of the restoration will be worth the enjoyment you get from the vehicle, or the price you think you could sell it for.