YOu certainly don't need a written report prepared by a private consultant.
I have seen heaps of appeals where the statement is in the form of a letter. Which basically covers the points that captain underpants said.
You should simply make your case - why do you think what you want to build should get permission? Why do you think that the Council's case is not strong?
A list of nearby developments is irrelevant unless you can demonstrate (through research at the planning department) that they set a valid precedent i.e. permission granted within the term of the current plan (or where the previous policy of the superseded local plan is largely similar to that of the current adopted local plan).
You can often access the policies of the local plan on-line these daays. Look at the policies referred to in the reason fro refusal and say why you think that they suggest that permission should be granted rather than refused. I.e. the proposal would NOT have an adverse impact on residential/visual amenity because.... (it would not overshadow neighbouring houses and gardens, it would not appear bulky or overdominant, it would not result in adverse visual impact and so on).
If you appeal and the appeal gets dismissed there is nothing to stop you applying for reduced or modified development and then appealing again if permission refused.
Basically, I have seen many appeals allowed despite the fact that they were submitted by the appellants rather than via a private consultant/agent. BEcause what the Inspector will do is look at the relevant policies, look at your arguments, and work out whether in his opinion, with ref to the policies and the proposal, the decision to refuse was reasonable. For you to put your case across you do not have to write as if you are a chartered planner, or to include extensive technical jargon.
But I can understand completely why appellants do get private consultants to write on their behalf - it does make one feel more confident if there is a "professional" writing in planning speak. Beware though that the quality of written appeal work can vary considerably. I have felt sorry for some appellants who have obviously paid a fortune for a statement that could have been written by themselves, and possibly with fewer glaring errors.