Surplus .303 is a mixed bag - much of the good stuff is gone, and what's mostly being marketed these days (ie, by AIM, Century, Sportsmansguide, etc) is POF, or Pakistani Ordnance Factory. Although made on British equipment, quality and process contol is much different, and there are the aforementioned hangfires. Remember, any surplus you buy is going to probably from the '60's, at the newest.
I have about 1500 rnds of mixed headstamp English .303 made in the '50s, and there are hangfires - click bangs, in popular Enfield parlance. They're good for breaking you of any bad habits - look at them as a live fire ball and dummy drill.
.303 is loaded commerically by several companies - Wolf Gold (made by PRVI Partisan), Hot Shot (Century's brand, I believe), and Remington UMC are 3 that come readily to mind. The only one of the bunch I've shot has been the Remington UMC 174 gr FMJ-BTs, and they were abysmal - I actually called Remington to complain. Every round out of multiple rifles keyholed. I later found out that Enfields are known to have problems stabilizing boat tailed bullets - something to keep in mind. Bullet diameter was .310, also, I've always been told it should be closer to .312.
If you have a reloading rig, get yourself a set of dies and have at it. Best thing I can recommend. There probably isn't any new .303 surplus that's going to come to light in the future - although I have to wonder if the Indians are sitting on a substantial stockpile they haven't surplused yet.