I'm sorry, but this story cannot be true - there are structural differences between a 2A/2A1 action and a No1 action - and yes, when PL made the assertion that 2A/2A1 actions were merely converted No1 .303 actions, I called him on it.
The easiest structural difference to see is that the ejector screw is moved forward approx. 1/4" on the 2A/2A1 action.
the second one is that there is a relief cut on the inside of the action to assist the cartridge base running into the ejector screw.
If .303 No1 receivers were "converted" into 2A/2A1 actions, it would be very plain to see, and there would be 2 ejector screw threaded holes in the action - similar to the Sterling 7.62 No4 conversion