Funny how people have different experiences....I've owned two nice Holland Royal Doubles, a 1952 vintage 500/465 and a 1904 vintage 500/450, still have the 500/450. I've put quite a few rounds down both and never had them come loose. I looked hard at a WR droplock and had JJ talk me out of it. His comment was "they are good for show not for go". I haven't owned any Purdeys but I've handled several and they felt heavy to me but to each their own. I own several Webley boxlocks and for overall reliability they would get my vote over any of the high end sidelocks.

So far all the quality, good condition English doubles I've had have been good investments. I've learned different things from all of them and haven't regretted buying any of them.

Have fun with your search, be selective and critical and you'll find a nice one. When you find it don't worry about a few bucks here or there, if it's nice and what you want, buy it. Quality and condition are always a good investment and easy to resell.