"The Family Doctor Association unites over 1000 UK GP practices that offer their patients continuity of care and the opportunity to see their own GP."The FDA says that they represent GP practices in the UK. There are 10,112 GP practices in the UK so they suggest that they represent 9.8% of GP practices. Their website list three levels of membership, depending on practice size: £150, £200 or £250. They are a registered educational charity (299871) and their accounts for 2011 show that their income from subscriptions were £109,762.
So that means they had between 439 and 731 members. Hardly over 1000.