I have some 1980's manufacture HXP .303 ammunition. I've heard that HXP made a run of the .303 ammo because the British were short on BREN guns converted to 7.62 NATO and they had planned to bring some .303 BREN guns out of storage if need be during the Falklands war.
HXP manufactures all sorts of ammunitio, with much of that sold to the military of other countries.
The 80's production HXP .303 does not use cordite and some who have examined the propellant say that its probably Winchester powder.
The bullets have a solid lead core, no lightweight nose plug as found in MkVII ammunition.