Officially, yes you should only talk to the dedicated contact person within the company. If they proceed with a dismissal then the first you should do is appeal it internally using the appeals procedure you will be told about. After that, your only option is to consider an unfair dismissal claim in the employment tribunal.
Before a person can make a claim in the employment tribunal, they would be required to participate in mandatory early conciliation through the Advisory Conciliation and Arbitration Service (ACAS).
The purpose of this process is to allow ACAS to mediate between the claimant and respondent to agree on an out of court settlement in order to avoid the need for legal action in tribunal. The respondent does not have to engage in these discussions, or if they do and the talks are unsuccessful, the claimant will be issued with a certificate allowing them to make a claim.
However, if a settlement is reached, the claimant would agree not to proceed with the claim in return for the agreed financial settlement. Other terms can also be agreed as part of the settlement, such as an agreed reference.
To initiate the conciliation procedure ACAS can be contacted online by filling in the following form (https://ec.acas.org.uk/Submission/SingleClaimantPage), or by phone on 0300(###) ###-####
If the conciliation process was not successful and you then wanted to make a formal claim in tribunal, you can do so here: