I agree with the value in buying through the small dealers who know the product. I have purchased about $33,000 worth of parts through British Car Specialists in the last 1-1/2 years and have been very happy (Yikes, I have not added it up before). Michael (parts manager) knows the products very well and can usually tell you how close to original the parts are. They also have had used parts available in some cases where new were not available. They are Moss and Kilmartin dealers, but also carry other rare hard to find parts and in some cases, more original parts. They offer a 10% discount to restorers when you make a large initial order.
By the way, I have no connection to them other than being a customer.
Paul