OEW numbers: A, 29,300 pounds. B, 32,000 pounds. C, 34,800 pounds.
So while the C has more span and more fuel than the A, it hauls an extra two and a half tons around, which won't help the range much.
The 2,700 pound diff between the A and the B is interesting because the B propulsion system itself is 4,000 pounds heavier, and I don't think that includes STOVL doors and actuators (because those weights are, I believe, those for which PW/RR are responsible).
So we're talking about a lot of weight having to be pared out of the rest of the B airframe (given that things like the IPP and the avionics are common). That's why the B is a 7g airframe and has slightly smaller H-tails and (I believe) flaperons. It does not have an internal gun, which also reduces OEW, but still it would be interesting to know how many structural bits are still common.
As for the C, the driver is a much bigger wing. 50 per cent bigger than the A/B and consequently bigger tails. Compare the Rafale C-to-M relationship and weep.