J

I can't answer you on buying a rifle from WR or H&H. My guess would be the rifle would have been checked over but its only a guess. It will be reflected in their prices most likely.

300 Sherwood for $5000. Just my personal opinion but I wouldn't buy a Sherwood for that, or really at all for that cartridge. But maybe you like it and it fits what you want then its your choice.

For $5000 I would look for a .450 Black Powder Express (or similar) where nitro for black loads could be used or even a .450/.400 NE may be possible. I'm sure you could find a medium calibre double in that price range too such as a 7mm or 8mm. Probably not a sidelock. UK prices may be a lot different too.

Good luck. I think if you look hard and wait for the right double you will find something that is right for you.