I've never dealt with Vintage football Shirts - but have bought from www.matchwornshirts.com
several times and you can see positive customer feedback from lots of customers on the site - I do believe they are planning to limited their business going forward
other good sellers are Serez.de for International and German Shirts
Urmyhero.co.uk for UK Shirts
Many people do rant about www.footballmatchshirts.co.uk/
- but personally I've never used - The site is full of shirts which have already been sold and its often difficult to tell if a shirt is match worn or player issued -I've tried contacting them at least twice in the past and been ignored.
That failing a good old fashioned search on ebay under "Match Worn" can often help you find a few gems.
In recent months I've found a match worn Michu shirt for around £170 and been offered £400 less than a week later as well as a Player Issued Team GB Jack Cork shirt for the same price... A few of these went for around the £400 mark too after the Olympics
If you ever buy a replica shirt - make sure you avoid UKSOCCERSHOP at all costs!!