I own a Bristol 19 (Sailstar Corinthian if made before about 1971). They are wonderful boats. They sail really well, and I like the feel of sitting so low in the water, that the below waterline cockpit gives. As with any boat pushing 40 years old, there may be some issues to look out for.
Check the chainplates for soundness and check that they are solidly bolted. Look closely at the condition of the rudder. My 67 Corinthian has a wooden rudder that is in good shape, but shows slight gaps where the pieces are joined, when it dries out. Put some pressure on the rudder to be sure nothing is too loose. Look around the rub rail and inside at the hull joint for collision damage and evidence of leaking. The gelcoat on my 19 had several little voids under it, that I had to dig out and fill. Nothing serious, and I think it was a manufacturing defect rather than blisters.
Keep in mind that the cockpits are not self bailing. You will need to keep a cover on at dockside, and should have a bilge pump for rainwater.
Good luck!