Hi Slim Peacock!
What's your first name? or is that what you prefer?
We have many members in the UK. the subject of opening a shop is not really something that can be summed up in one post.
I think that you have to look first at your business plan - and what void would you fill that is not already there and makes you unique - before you source suppliers. In this business, suppliers tend to find you when you get your good reputation out there, unlike other areas of retail. The word does get out . Since vintage is not unlimited most times, no seller is going to give you names of the people that supply them. And one that might work for them, may not have anything for you based on your tastes. Also, really focus on what your idea of "best stuff" is. To some folks nothing newer than 1920 is considered anything special. For some its couture, for some its mint condition 80s wear. And to some its anything as long as its in top condition. It really doesn't matter - just find where your focus is so you have some sort of identity to promite.
Chris