Hi Simon,
To kick this off, first item, cans. Not the two gallon can, which were quite hardy, I regularly use one made in 1936, never leaked. It is the 4 gallon "flimsy", that I think they were refering to, more petrol was lost from these leaking cans than was used.........maybe an exageration, but from what I understand a large percentage was wasted.
Second item, true, everything had to suit the British loading guage, which took into account bridges and tunnels, not just track spacing.