The range of F-35B is not conclusively known, but at the very least, we know that it is possible that it will have a longer range than the EF, despite being a VSTOL fighter.
Until it comes into productive service, the F35's longer range than the EF is purely theoretical and of no practical use whatsoever ...... Let me see, do I want a range of X miles now or should I wait 10-15 years for a jet with range 2X miles? Well, I would hazard to suggest that the troops on the grd in AF would be more than happy to take the EF with its X range next year rather than wait for the F35's 2X range.
Plus, the way things are panning out and given the likely future strategic priority for UK Plc being AF rather than IZ, I would think that the EF's range is plenty enough to get from KAF or KAIA down to Helmand with enough ordnance to do some landscaping.