Still have to pay the court fee though so I'd still recommend another last attempt to resolve prior to court.
BUT that is added to the outstanding bill plus you can add interest.
As Binky says most people will pay up before you start the proceedings ............ the wording of you final demand needs to include the following:
"I attach my original invoice to this letter and wish to inform you, that if the invoice is not settled in full by xxxx xxxxxxx 2020, I intend to refer this matter to the Small Claims Court without further reference to you.
Please be aware that all costs associated with such action are added to your outstanding bill and will make the final payment higher."