Thanks everyone for the replies , no way I'd get throug h the build without the help here !
So I think the best option is going to be new transformer, with the cost of the drives at risk, and fact I'd prefer the simplest approach !
So to be 100% here, 60v or 55v to be safer if supply varies to high side . Will I lose much power @ 55V? And stick with 750VA?
Will PM you about other transformer if interested jazz.