I did the appeal myself - putting in some common sense arguments for why it should be approved (e.g. precedent, no neighbour objections etc). After popping down to the planning dept and speaking to a different planner he didn't see any particular reason the first application was declined so we knew it was a borderline decision. At the same time we submitted slightly altered plans (to account for the concerns causing the original application to be rejected) in case the appeal was rejected - so not to delay the building work any further. In the end the appeal was accepted and the revised plans were approved.