I'm not sure really apart from a bargaining chip what the worry about a set of missed stamps from 8 years ago is? Before I serviced mine I took it to a great indy but frequently forgot to get the book stamped, a few owners down the line and that detail is lost and all you know is there's no stamps! Realistically it's been fine for the past x years so it's not a big deal. Condition is key, by all means use this as a lever but if the condition is excellent then go for it, you'll easily waste the £1000 on a car that isn't in great condition so don't save money to just spend it later. Check underneath for rust the w brace is usually easy to see. Listen for metallic clunks at low speed when driving especially over bumps, listen for a smooth start up etc.
If you do go see it be prepared to walk away if it's not for you! They're not in short supply so don't be fooled into thinking this is a one off chance!