I'd recommend you look into the most minute detail of the bass you want - there's more to it than the cosmetics and electronics; weight, neck shape at the xx fret, pick up placement can be just as important. Best thing you can do is have a checklist ready with everything you can possibly think of and then have a chat with the luthier.
I doubt you would ever end up with something worse than a 'regular' off the shelf bass - unless it's a crazy build, but I suppose there's always a chance that the ideal bass in your head doesn't really do it for you when it's in your hands. Although I'm not speaking from experience on that particular point.
If you want to go British I couldn't recommend Jon Shuker highly enough.