“To comply with its duty to act fairly unders.33(1) of the Arbitration Act 1996 , the tribunal should give the parties an opportunity to deal with any issue which will be relied on by it as the basis for its findings. The parties are entitled to assume that the tribunal will base its decision solely on the evidence and argument presented by them prior to the making of the award. If the tribunal is minded to decide the dispute on some other basis, the tribunal must give notice of it to the parties to enable them to address the point. Particular care is needed where the arbitration is proceeding on a documents-only basis, or where the opportunity for oral submissions is limited. That said, a tribunal does not have to refer back to the parties its analysis or findings on the evidence or argument before it, so long as the parties have had an opportunity to address all the “essential building blocks” in the tribunal’s conclusion. Indeed, the tribunal is entitled to derive an alternative case from the parties’ submissions as the basis for its award, so long as an opportunity is given to address the essential issues which led the tribunal to those conclusions…”