I wouldn't worry about ^corrosive^ primers.
They aren't really corrosive. They leave a residue behind which absorbs moisture from the air which can lead to rust. Prompt cleaning and oiling avoids this problem. The main problem might be in finding the proper Berdan primers.
The LGS used to stock them pre-covid, but I don't know the current situation.
The American military used corrosive primers for quite a few years, for their match ammo, after switching to non corrosive primers for their regular ammunition, because they were more highly developed and gave better accuracy.
You might want to examine your .303 loading goals. The .303 could become, if not addicting, then certainly habit forming. I spent about half of last year's casting, loading, and shooting efforts trying to resuscitate a rather wretched 1896 Long Lee . I don't see myself being cured for this season, either.
So, loading for the .303 is much like acquiring a taste for 12 year old Scotch. It's not necessarily bad, but could be expensive, and possibly get out of control. I have some .30/30 and. 38/55 single shot rifles that haven't been fired in 3 years.