I've read all the Posts.
Purchasing a a firearm for most of us is a very personal matter. Selling for many has become a business matter.
The original Poster is not someone I would like to do business with by the reading and intent of the original Post.
26" barrel is not a reason to return a firearm.
But and this is the BIG BUT, the 3-day inspection period is just that, a 3-day period to inspect and return the firearm. Why, because a description, even with numerous pictures is simply not good enough to disclose all. The 3-days is not an allowance to head to the range and shoot the gun until you are satisfied/dissatisfied although I know of individuals that have done that and dealers that have accepted returns based on that.
The gun should be returned at the purchasers expense and I at least would not have dealings with the purchaser. In terms of damages, I think a British Court would have allowed the purchaser 2 pennies in the past. -Dick