Design - showed a tendency to an experimental design as opposed to an operational design. The staggered engines reduced drag but servicing of the upper engine usually required removal of the lower engine.
Not true, four years as an engine man on Lightnings and never removed one to service the other.
Fuel, or rather the shortage thereof - which to be fair was the bane of most of the early jets but something that was so much more pronounced in the Lightning due to the inability to carry underwing tanks and the prodigious consumption of the Avons, 10 minutes from full to dry tanks if the pilot stayed in full reheat.
It was short of fuel and I have had to refuel on the reheat pan whilst testing. No underwing tanks, but we did fit overwing tanks.