if an employee appeals to her employer against a decision to dismiss her, is then 'suspended without pay' until the internal appeal has been concluded, then wins the appeal and is reinstated, the original dismissal 'vanishes' and she will therefore be entitled, subject to any contract term to the contrary, to full back pay for the period of the suspension. However in such circumstances the employee will not be able to claim unfair dismissal because she has not been dismissed.
For relevant general notes see Unfair dismissal/reinstatement and reengagement orders/effect on continuity of employment and/or Suspension of employee/general .