There is no legal aid available for representation at Employment Tribunals, except occasionally for very complex cases, although basic preliminary advice can sometimes be obtained under the Legal Help Scheme. This provides a short session with a solicitor to talk through any legal issue on a preliminary basis.
You should be aware that the Employment Tribunal does have the power to award costs against you at a tribunal, although this power is only very rarely exercised (in about 3% of cases that make it to a hearing). Individuals are most at risk of having costs awarded against them if it is considered that the claim had little merit or possibility of success, or the claim has been brought in an unreasonable manner.
The Conservative-led Government proposes that the maximum amount that a tribunal be able to award against the losing party be increased to £20,000 (plus payment of the tribunal’s own costs).