What was your employment status at the company? Employed or self-employed/Ltd co. contractor?
It makes a difference as to which route you can take. Normally an employee/ex-employee has to go via the Employment Tribunal in the case of unpaid wages/un-agreed deductions. If you are self-employed then you are just another debtor who has to go via the courts.
Worth seeing if you can find out who else they owe. It's possible they owe so much that the legal costs you incur will be good money after bad.