So we were saying mostly the same thing. That's a good start :)

I think I've worked out where my mental block is for this element at least. I was treating parallel as increasing A rather than decreasing the division of A. In other words, I was thinking of two outputs, each with 50V 625VA. Parallel would make this one output of 50V 1250VA. Rather, I should be looking at it as two outputs of 50V sharing 625VA between them - effectively making it 100V / 625VA = 6.2A. Wiring it in parallel would then have the same VA but divided by less, which has the same end effect as doubling it: 50V / 625VA = 12.5A. When I look at it like this, your previous comments make more sense so I guess I'm on the right track.

And you wonder why I get jittery with mains power