Greek HXP (usually 1970's headstamp) has always been great ammo for me. I'm on my last few bandoleers of it but have been reloading the excellent HXP brass for some years now.
Reloading is the way to go as far as I'm concerned. A set of new dies or even a used set in the common calibers is easy to find. I've used alot of pulled AK bullets in 303 w/excellent results too.
I'd be a little wary of any 'POF' made and packaged 303 Brit ammo.
That's Pakistani mfg'r stuff (Pakistani Ordnance Factory) and to be kind,,it doesn't have the greatest reputation.
Lots of hang fire & duds. Strange smell and dirty when it does fire.
A lot may be due to prior handling and storage in less than perfect conditions over there. Maybe it's just bad stuff to begin with.
Some have reported good results with POF made ammo,,but the majority opinion is negative. My trials with it were negative. It was click-bang ammo that was good if you were trying to teach someone not to flinch. It was $1.50/box IIRC and that goes back a ways.
So the stuff has been around for quite a while. They're probably still making it for all I know!.
The stuff got all sorts of nick-names for the 'POF' initials, like Pride of Frankenstein, and others that I can't list here for for fear of being shown the exit door.
Old lots of War time 303 are just about gone and have begun to be priced for collectors instead of shooters anyway. Anything WW2 dated you can expect corrosive primers. Not a big deal really,,just clean properly.