I was recently in the same situation as you, wanting a 'best' grade English s/s. I live in the UK, and visited a number of dealers, looking at several guns. It was several months and many views before I eventually 'bought'.
My advise would be to look at, handle, shoot if possible as many guns as possible. The reason is quite hard to put in words, but these guns are often old, and may have seen a lot of use, with many repairs, tightenings, possible abuse etc.
As you gain experience, you notice a difference in 'feel' from one to another. Some feel loose and well worn .... and clearly need money spending. Others are 'tight and pristine' - too much so in some cases. Some that are tight are just plain 'stiff' and not smooth to operate. My guess is that these have had a quick tighten and will be loose again soon.
Some however are neither overly tight nor loose, but silky smooth in operation. These often (usually even) have some genuine handling wear and usage marks, worn blueing, worn chequering, a few bruises on the stock, but the screw (pin) heads are undamaged, slots line up, wood to metal is tight etc. Often, these are the guns with around 100 years of genuine careful use and proper maintenance .... not bodged, not over-restored, not worn out. With one of these, you can restore to your own satisfaction, with your chosen craftsman, as much, or as little as you like.
In my view, this is the kind of gun to look for, and its only by getting plenty of experience that you may get to recognise what feels just plain worn out, what feels just freshly tightened and what feels just plain 'right'.
I ended up with a lovely gun, shows genuine wear and has had some properly done work over its 100 year life, but it feels as nice and smooth and 'genuine' as any gun I have ever handled, and having had it for a little while now, no nasty surprises have emerged.
Good luck, do plenty of looking and handling and follow your instincts!
