There is a difference between translation and legal aid services. Even if you were given permission to have a translator, he would only technically translate words, but he would not explain anything in legal terms as the translator is not a legally qualified person. Your English seems quite good, are you sure you needed a translator at all? It looks like you, in fact, wanted someone to explain the meaning of what is going on at court, which is called “legal aid”, however, the translator would not be able to provide this.
If you want a free legal aid instead, the requirements differ. Here is a calculator to check if you are eligible for it - https://civil-eligibility-calculator.justice.gov.uk/
Your case is at court, not tribunal, then the judge has discretion to decide if he wants to grant you a free translator or not, based on the whole picture and on all circumstances of the case. There are no strict rules how the judges’ decision shall be made. By law, judges have wide discretion.
Here are some precedents from tribunals practice, it may help for understanding how courts consider applications for translating services. In Hak v St Christopher's Fellowship  ICR 411,  IRLR 342, the EAT considered the duties of a Tribunal to ensure a fair hearing for a litigant whose first language was not English. In general, where a party wishes to have an interpreter present, the Tribunal should facilitate it as best it can and should “strive to do so” (para 38). However, there may be circumstances in which the command of English is so poor that a litigant cannot give the account which they would wish to give to the Tribunal. There is, in such cases, a powerful argument that the Tribunal must take all reasonable steps – including funding – to secure the services of an interpreter (para 39). By contrast, where a litigant had a well-demonstrated ability to speak, write and read English, an interpreter would be unnecessary and the request should be refused (but the Tribunal should “think long and hard” before so concluding in respect of a person whose mother tongue may well not be English (para 40)). There were also cases, falling between these categories in which the Tribunal had to conduct an assessment of need, against achieving justice, fairness and equality of arms. This assessment was for the Judge bearing in mind that spoken and written language are different and that pressures in court are such that immediate comprehension and response are required (para 41). A useful test would be to ask whether the litigant's command of language was sufficient to enable him to give the best account to the tribunal which he would wish to give relating to the matters in dispute (para 45). See also Lema v DHL Supply Chain Ltd(UKEATPA/0315/17/LA), 21 March 2018 and Ringway Infrastructure Services Ltd v Conlon(UKEAT/0256/18/DA) in which it was determined that the claimant's command of English was sufficient that no interpreter was required.
You received a direction instead of an order because of the format of the application you have made. You may submit an application for the court to reconsider its decision.