As Ballsout said,- the plaint-fee varies according to the amount claimed.
Neither party can claimany other legal fees, except an "expert report" (usually with respect to claims for faulty workmanship/materials/tech. issues) this is capped at ~£200.
If the defendant loses/does not file a defence (loses by default) the cost of the case is added onto his bill, plus you get to nail him for your time/fuel/fare wasted going to court.
warning! Make sure you send written warning that, unless you have full settlement within "X" days (7 is enough at this stage) you will take legal proceedings for recovery without further warning.
then do it!...court even has a DIY kit of leaflets, explaining all the stages and how to complete the forms.
Last "tricky-dicky" I took, had to pay the lot, plaint-fee, expenses and expert report cost. it also cost him about 5 solicitor's letters whilst he tried to frighten me into giving -up.
his only satisfaction ,- he had the hearing transferred from my local court, to his....the defendant is allowed to move the hearing to where the alleged incident took place, I believe.....but then it cost him more expenses for me to travel!