Those are nice chairs, but you wouldn't pay over $200 in the San Francisco area for them. I'd guess 1940s to '50s also, and I could be wrong.

1940-50s Chippendale-influenced? The knotwork on the slats is both French and Chippendale. Probably walnut or "fruitwood". Old, but not "antique". My mum's era, not great-granny's.

They are nice chairs, but not great antiques, especially if the "not perfect" includes any wobbles. A set of 8 is rare. They usually were split up, damaged or lost. He could probably make more by selling 2 sets of 4.

What would similar chairs cost new from a mid-range shop? That's your starting point for negotiating a price. Is 75 GBP a good price for a chair? And do you really need 8 chairs - if so, getting 8 might warrant a higher price.

Here's a UK Craigslist ad: http://london.craigslist.co.uk/atq/3949543208.html 800GP for 8 vintage chairs (2 closely matches sets of 4) so it's not unreasonable in your area.

That sort of seat is a doddle to reupholster, so you might offer 65 a chair and do it yourself, since he's not including fabric. 4 screws hold a padded piece of wood to the base. Remove the screws, remove the faded velvet, and staple on a new cover. Take the time while the seat is off to give them a good polish.